Special counsel Robert Mueller is set to give the first public insight into how much information President Donald Trump's former national security adviser has shared with prosecutors in the Russia investigation.

The special counsel is facing a Tuesday deadline in Michael Flynn's case to file a memorandum recommending a sentence and providing a federal judge with a description of how valuable the retired U.S. Army lieutenant general has been to the probe.

The deadline comes ahead of Flynn's Dec. 18 sentencing and more than a year after he pleaded guilty to lying to the FBI about reaching out to Russian government officials on Trump's behalf.

Federal sentencing guidelines recommend between zero and six months in prison for Flynn, leaving open the possibility of probation.

The detailing of at least some of Flynn's cooperation also comes as Trump has increasingly vented his anger at the probe - and at one of his former confidantes who cooperated with it.

ASSOCIATED PRESS

Washington - 10 July 2018

1. Mid pan, Michael Flynn exits SUV enters courthouse

2. Close-up pan, Michael Flynn exits courthouse as protesters shout

ASSOCIATED PRESS

Washington, D.C. - 1 December 2017

3 . Mid, pan Michael Flynn exits court and gets into car, car drives away as protesters shout (English) "Lock him up. Lock him up. Lock him up. Convicted criminal. Criminal. Lock him up. Lock him up. "

4. Side view, Flynn exiting court

ASSOCIATED PRESS

Washington, DC - 1 February 2017

5 . Various of former National Security Advisor Michael Flynn at lectern

6. SOUNDBITE (English) Michael Flynn, National Security Advisor

US POOL

Washington, DC - 20 January, 2017

7. Michael Flynn arrives at inauguration

ASSOCIATED PRESS

New York - 1 December, 2016

8. Michael Flynn walks into Trump Tower with Robert Gates, U.S. Defense Secretary under President George W. Bush and Barack Obama

Special Counsel Robert Mueller is using a grand jury in Washington as part of an investigation into potential coordination between the Trump campaign and Russia, a person familiar with the probe said Thursday.

The use of a grand jury, a standard prosecution tool in criminal investigations, suggests that Mueller and his team of investigators are likely to hear from witnesses and demand documents in the coming weeks and months. The person who confirmed to The Associated Press that Mueller had turned to a grand jury was not authorized to discuss the investigation by name and spoke on condition of anonymity.

The Wall Street Journal first reported the use of a grand jury.

Grand juries are common vehicles to subpoena witnesses and records and to present evidence, though they do not suggest any criminal charges are near or will necessarily be sought. It was not immediately clear how or whether the Washington grand jury was connected to the work of a separate one in Alexandria, Virginia. That panel has been used to gather information on Michael Flynn, Trump's former national security adviser.

A spokesman for Mueller's team did not return an email seeking comment.

Mueller's reliance on a grand jury is the "logical next step in this investigation" given that it's the traditional method for prosecutors to gather evidence, said Washington defense lawyer Jacob Frenkel.

Meanwhile, lawyers for President Donald Trump said they were unaware of the existence of a grand jury and had no information to suggest the president himself was under federal investigation.

"With respect to the news of the federal grand jury, I have no reason to believe that the president is under investigation," defense attorney John Dowd told the AP.

Ty Cobb, special counsel to the president, said he wasn't aware Mueller had started using a new grand jury.

"Grand jury matters are typically secret," Cobb said. "The White House favors anything that accelerates the conclusion of his work fairly. ... The White House is committed to fully cooperating with Mr. Mueller."

It was not clear what witnesses might appear before the grand jury or what evidence it might be accumulating or presented with.

Mueller was appointed special counsel in May by the Justice Department following the firing by Trump of FBI Director James Comey. He has since assembled a team of more than a dozen investigators, including current and former Justice Department prosecutors with experience in international bribery, organized crime and financial fraud.

That team has been working at an undisclosed location in Washington, so presenting evidence inside a federal courthouse in the city could be more convenient for the group of investigators than working out of Alexandria. Mueller also worked as a prosecutor in Washington before becoming FBI director, a job he held for 12 years.

A grand jury "increases the power of the prosecutors," said David Levine, law professor at the University of California Hastings College of Law. "Instead of asking for people to provide testimony, they can demand testimony under the penalty of perjury and under risk of contempt of court. And with respect to documents, instead of asking people for documents, they can demand documents. And so for example the tax returns, a subpoena can unlock those tax returns," he said.

News of the grand jury came as senators introduced two bipartisan bills aimed at protecting Mueller from being fired by Trump, with both parties signaling resistance to any White House effort to derail the investigation into Russian meddling in last year's election.

Trump's defense team has been looking into potential conflicts of interest among members of Mueller's team, such as past political contributions to Democrats including Hillary Clinton, and Trump has warned that any effort by Mueller to look into his finances would fall outside the scope of Mueller's appointment.

Under the regulations, Deputy Attorney General Rod Rosenstein is the government official empowered to fire Mueller under limited circumstances, such as conflict of interest and dereliction of duty. Rosenstein, who appointed Mueller, has publicly said he has seen no basis for firing him.

Oakland, California - Aug. 3, 2017

1. David Levine looks at news story on phone

2. Screen showing news story about grand jury in Russia probe

3. SOUNDBITE (English) David Levine, law professor, University of California, Hastings College of the Law

++ covered by video ++ "What we've learned is that special counsel Mueller and the lawyers working with him ++ are using a grand jury to further their investigation into the questions about Russian collusion and related areas such as financial transactions and other matters."

Washington, D.C. - June 21, 2017

4. AP Photo of former FBI director Robert Mueller arriving for meeting at Capitol Hill

Oakland, California - Aug. 3, 2017

5. SOUNDBITE (English) David Levine, law professor, University of California, Hastings College of the Law

++ covered by video ++ "It increases the power of the prosecutors. ++ Instead of asking for people to provide testimony, they can demand testimony under the penalty of perjury and under risk of contempt of court. And with respect to documents, instead of asking people for documents, they can demand documents. And so for example the tax returns, a subpoena can unlock those tax returns."

Huntington, West Virginia - Aug. 3, 2017

6. AP Photo of President Donald Trump speaking at rally

Washington, D.C. - Dec. 11, 1998

7. AP Photo of President Bill Clinton walking to Rose Garden to deliver statement on impeachment

Oakland, California - Aug. 3, 2017

8. SOUNDBITE (English) David Levine, law professor, University of California, Hastings College of the Law

++ covered by video ++ "If it's somebody in the United States, they are subject to subpoena. And that would include the president of the United States. Famously President Bill Clinton appeared before a grand jury. It turned out not very well for him."

Oakland, California - Aug. 3, 2017

9. SOUNDBITE (English) David Levine, law professor, University of California, Hastings College of the Law

"We're probably months and months away before we hear formally ++ covered by video ++ from Mr. Mueller as to whether and who might be indicted and for what." ++

Washington, D.C. - June 21, 2017

10. AP Photo of former FBI director Robert Mueller arriving for meeting at Capitol Hill

Special Counsel Robert Mueller is using a grand jury in Washington as part of an investigation into potential coordination between the Trump campaign and Russia, a person familiar with the probe said Thursday.

The use of a grand jury, a standard prosecution tool in criminal investigations, suggests that Mueller and his team of investigators are likely to hear from witnesses and demand documents in the coming weeks and months. The person who confirmed to The Associated Press that Mueller had turned to a grand jury was not authorized to discuss the investigation by name and spoke on condition of anonymity.

The Wall Street Journal first reported the use of a grand jury.

Grand juries are common vehicles to subpoena witnesses and records and to present evidence, though they do not suggest any criminal charges are near or will necessarily be sought. It was not immediately clear how or whether the Washington grand jury was connected to the work of a separate one in Alexandria, Virginia. That panel has been used to gather information on Michael Flynn, Trump's former national security adviser.

A spokesman for Mueller's team did not return an email seeking comment.

Mueller's reliance on a grand jury is the "logical next step in this investigation" given that it's the traditional method for prosecutors to gather evidence, said Washington defense lawyer Jacob Frenkel.

Meanwhile, lawyers for President Donald Trump said they were unaware of the existence of a grand jury and had no information to suggest the president himself was under federal investigation.

"With respect to the news of the federal grand jury, I have no reason to believe that the president is under investigation," defense attorney John Dowd told the AP.

Ty Cobb, special counsel to the president, said he wasn't aware Mueller had started using a new grand jury.

"Grand jury matters are typically secret," Cobb said. "The White House favors anything that accelerates the conclusion of his work fairly. ... The White House is committed to fully cooperating with Mr. Mueller."

It was not clear what witnesses might appear before the grand jury or what evidence it might be accumulating or presented with.

Mueller was appointed special counsel in May by the Justice Department following the firing by Trump of FBI Director James Comey. He has since assembled a team of more than a dozen investigators, including current and former Justice Department prosecutors with experience in international bribery, organized crime and financial fraud.

That team has been working at an undisclosed location in Washington, so presenting evidence inside a federal courthouse in the city could be more convenient for the group of investigators than working out of Alexandria. Mueller also worked as a prosecutor in Washington before becoming FBI director, a job he held for 12 years.

A grand jury "increases the power of the prosecutors," said David Levine, law professor at the University of California Hastings College of Law. "Instead of asking for people to provide testimony, they can demand testimony under the penalty of perjury and under risk of contempt of court. And with respect to documents, instead of asking people for documents, they can demand documents. And so for example the tax returns, a subpoena can unlock those tax returns," he said.

News of the grand jury came as senators introduced two bipartisan bills aimed at protecting Mueller from being fired by Trump, with both parties signaling resistance to any White House effort to derail the investigation into Russian meddling in last year's election.

Trump's defense team has been looking into potential conflicts of interest among members of Mueller's team, such as past political contributions to Democrats including Hillary Clinton, and Trump has warned that any effort by Mueller to look into his finances would fall outside the scope of Mueller's appointment.

Under the regulations, Deputy Attorney General Rod Rosenstein is the government official empowered to fire Mueller under limited circumstances, such as conflict of interest and dereliction of duty. Rosenstein, who appointed Mueller, has publicly said he has seen no basis for firing him.

Oakland, California - Aug. 3, 2017

1. David Levine looks at news story on phone

2. Screen showing news story about grand jury in Russia probe

3. SOUNDBITE (English) David Levine, law professor, University of California, Hastings College of the Law

"What we've learned is that special counsel Mueller and the lawyers working with him are using a grand jury to further their investigation into the questions about Russian collusion and related areas such as financial transactions and other matters."

Washington, D.C. - June 21, 2017

4. AP Photo of former FBI director Robert Mueller arriving for meeting at Capitol Hill

Oakland, California - Aug. 3, 2017

5. SOUNDBITE (English) David Levine, law professor, University of California, Hastings College of the Law

"It increases the power of the prosecutors. Instead of asking for people to provide testimony, they can demand testimony under the penalty of perjury and under risk of contempt of court. And with respect to documents, instead of asking people for documents, they can demand documents. And so for example the tax returns, a subpoena can unlock those tax returns."

Huntington, West Virginia - Aug. 3, 2017

6. AP Photo of President Donald Trump speaking at rally

Oakland, California - Aug. 3, 2017

7. SOUNDBITE (English) David Levine, law professor, University of California, Hastings College of the Law

"If it's somebody in the United States, they are subject to subpoena. And that would include the president of the United States. Famously President Bill Clinton appeared before a grand jury. It turned out not very well for him."

Washington, D.C. - Dec. 11, 1998

8. AP Photo of President Bill Clinton walking to Rose Garden to deliver statement on impeachment

Oakland, California - Aug. 3, 2017

9. SOUNDBITE (English) David Levine, law professor, University of California, Hastings College of the Law

"If I was in the White House, I would be concerned that the investigation has gone up a notch or appears to have gone up another notch. In short order probably people who are in the administration or former members of the administration or former members of the campaign will be getting subpoenas to testify and provide documents."

Washington, D.C. - June 21, 2017

10. AP Photo of former FBI director Robert Mueller arriving for meeting at Capitol Hill

Oakland, California - Aug. 3, 2017

11. SOUNDBITE (English) David Levine, law professor, University of California, Hastings College of the Law

"And as the word gets around in the White House as to who is getting subpoenas and what is being asked, at least some members of the administration will obviously be getting more more nervous. This is why so many of them already have - the parlance is they've lawyered up. So many of those senior officials each have their own lawyer or series of lawyers because of their concerns of where this may lead."

Huntington, West Virginia - Aug. 3, 2017

12. AP Photo of President Donald Trump speaking at rally

Oakland, California - Aug. 3, 2017

13. SOUNDBITE (English) David Levine, law professor, University of California, Hastings College of the Law

"We're probably months and months away before we hear formally from Mr. Mueller as to whether and who might be indicted and for what."

14. David Levine looking at phone

Former national security adviser Michael Flynn has arrived at the federal courthouse in Washington ahead of his sentencing hearing.

Flynn is to be sentenced at 11 a.m. on Tuesday for lying to the FBI about contacts with the Russian ambassador to the United States.

He'll be the first White House official punished in special counsel Robert Mueller's investigation into potential coordination between the Trump campaign and Russia.

Prosecutors with special counsel Robert Mueller's office are not seeking any prison time for Flynn, citing extensive cooperation that has included 19 meetings with investigators.

The sentencing decision will be up to U.S. District Judge Emmet Sullivan.

Washington - 18 December 2018

1. Michael Flynn walks through crowd and into courthouse

2. Protesters outside courthouse

Former national security adviser Michael Flynn has arrived at the federal courthouse in Washington ahead of his sentencing hearing.

Flynn is to be sentenced at 11 a.m. on Tuesday for lying to the FBI about contacts with the Russian ambassador to the United States.

He'll be the first White House official punished in special counsel Robert Mueller's investigation into potential coordination between the Trump campaign and Russia.

Prosecutors with special counsel Robert Mueller's office are not seeking any prison time for Flynn, citing extensive cooperation that has included 19 meetings with investigators.

The sentencing decision will be up to U.S. District Judge Emmet Sullivan.

Washington - 18 December 2018

1. Michael Flynn walks through crowd and into courthouse

2. Protesters outside courthouse

Former national security adviser Michael Flynn has arrived at the federal courthouse in Washington ahead of his sentencing hearing.

Flynn is to be sentenced at 11 a.m. on Tuesday for lying to the FBI about contacts with the Russian ambassador to the United States.

He'll be the first White House official punished in special counsel Robert Mueller's investigation into potential coordination between the Trump campaign and Russia.

Prosecutors with special counsel Robert Mueller's office are not seeking any prison time for Flynn, citing extensive cooperation that has included 19 meetings with investigators.

The sentencing decision will be up to U.S. District Judge Emmet Sullivan.

Washington - 18 December 2018

1. Michael Flynn walks through crowd and into courthouse

2. Protesters outside courthouse

Former Trump administration national security adviser Michael Flynn is admitting in a statement that his actions were wrong, and he says his guilty plea is in the best interests of his family and the country.

Flynn released a statement Friday after pleading guilty to lying to the FBI about his contacts during the postelection transition period with the Russian ambassador.

AP reporter Chad Day recounts Flynn's appearance in a D.C. District Court Friday, before U.S. District Court Judge Rudolph Contreras.

Flynn says he's cooperating with an investigation led by special counsel Robert Mueller and his team of prosecutors.

That investigation is examining potential contacts between the Trump campaign and Russia.

Flynn also says he's been subjected to false accusations.

Washington, D.C. - 1 December 2017

1. Side view, Michael Flynn arriving at side of court house

2. SOUNDBITE (English) Chad Day, The Associated Press:

"So, this morning former national security adviser Michael Flynn appeared with his attorneys here at the Federal District courthouse in Washington and pleaded guilty to a charge of making false statements to FBI agents. Now this plea had been expected, there had been some movements over the last few days that indicated he was making a deal and today Flynn said that in exchange for his plea he is going to cooperate with Special Counsel Robert Mueller as part of his investigation into possible collusion with Trump associates and Russia during the 2016 presidential campaign. One of the main things that came out in the courtroom today and in court papers that were unsealed today is that Flynn has admitted that during December of last year before President Trump came into office, during the transition period, transition officials directed him to make contact with Russian officials about two specific issues. One was the response to U.S. sanctions that were imposed by President Obama in response to Russian election interference. And the other was for a U.N. Security Council resolution. Now, this is the first time that we've actually seen Flynn appear and talk about what happened and some of the things that were being investigated by Special Counsel Robert Mueller and so some of the unanswered questions that we have right now are you know who are these Trump transition officials that were directing his work at that time? And is he possibly cooperating with the government against them or providing information that could be used against them? Today in the courtroom, Flynn appeared and he spoke in a soft voice. He answered several questions that you usually have in these types of hearings. It was a very routine type plea hearing and then shortly after 11:00 today he said those words guilty and pled to this charge. Now this is a felony charge. And so but we don't yet know what this means in terms of whether he'll face any kind of prison time. The maximum for this charge is five years. But, we won't know a lot of that until a later date when they sentence him. "

3. Mid view, front of court house

4. SOUNDBITE (English) Chad Day, The Associated Press:

"So the main unanswered question now is you know coming out of this plea is who's next that Robert Mueller is looking at? You know when you're looking at the plea agreement, there are at least two transition officials that had phone calls with Michael Flynn that he later lied to FBI agents about. And so you know at this point all we know is that they have filed charges against him or a charge against him and that he's pled guilty to that. But there are a lot of indications and as we continue to mine these, these documents that the investigation is moving closer and closer to people in the Trump inner circle."

5. Pan, Flynn departing

Former Trump administration national security adviser Michael Flynn is admitting in a statement that his actions were wrong, and he says his guilty plea is in the best interests of his family and the country.

Flynn released a statement Friday after pleading guilty to lying to the FBI about his contacts during the postelection transition period with the Russian ambassador.

AP reporter Chad Day recounts Flynn's appearance in a D.C. District Court Friday, before U.S. District Court Judge Rudolph Contreras.

Flynn says he's cooperating with an investigation led by special counsel Robert Mueller and his team of prosecutors.

That investigation is examining potential contacts between the Trump campaign and Russia.

Flynn also says he's been subjected to false accusations.

Washington, D.C. - 1 December 2017

1. Side view, Michael Flynn arriving at side of court house

2. SOUNDBITE (English) Chad Day, The Associated Press:

"So, this morning former national security adviser Michael Flynn appeared with his attorneys here at the Federal District courthouse in Washington and pleaded guilty to a charge of making false statements to FBI agents. Now this plea had been expected, there had been some movements over the last few days that indicated he was making a deal and today Flynn said that in exchange for his plea he is going to cooperate with Special Counsel Robert Mueller as part of his investigation into possible collusion with Trump associates and Russia during the 2016 presidential campaign. One of the main things that came out in the courtroom today and in court papers that were unsealed today is that Flynn has admitted that during December of last year before President Trump came into office, during the transition period, transition officials directed him to make contact with Russian officials about two specific issues. One was the response to U.S. sanctions that were imposed by President Obama in response to Russian election interference. And the other was for a U.N. Security Council resolution. Now, this is the first time that we've actually seen Flynn appear and talk about what happened and some of the things that were being investigated by Special Counsel Robert Mueller and so some of the unanswered questions that we have right now are you know who are these Trump transition officials that were directing his work at that time? And is he possibly cooperating with the government against them or providing information that could be used against them? Today in the courtroom, Flynn appeared and he spoke in a soft voice. He answered several questions that you usually have in these types of hearings. It was a very routine type plea hearing and then shortly after 11:00 today he said those words guilty and pled to this charge. Now this is a felony charge. And so but we don't yet know what this means in terms of whether he'll face any kind of prison time. The maximum for this charge is five years. But, we won't know a lot of that until a later date when they sentence him. "

3. Mid view, front of court house

4. SOUNDBITE (English) Chad Day, The Associated Press:

"So the main unanswered question now is you know coming out of this plea is who's next that Robert Mueller is looking at? You know when you're looking at the plea agreement, there are at least two transition officials that had phone calls with Michael Flynn that he later lied to FBI agents about. And so you know at this point all we know is that they have filed charges against him or a charge against him and that he's pled guilty to that. But there are a lot of indications and as we continue to mine these, these documents that the investigation is moving closer and closer to people in the Trump inner circle."

5. Pan, Flynn departing

Former Trump administration national security adviser Michael Flynn is admitting in a statement that his actions were wrong, and he says his guilty plea is in the best interests of his family and the country.

Flynn released a statement Friday after pleading guilty to lying to the FBI about his contacts during the postelection transition period with the Russian ambassador.

AP reporter Chad Day recounts Flynn's appearance in a D.C. District Court Friday, before U.S. District Court Judge Rudolph Contreras.

Flynn says he's cooperating with an investigation led by special counsel Robert Mueller and his team of prosecutors.

That investigation is examining potential contacts between the Trump campaign and Russia.

Flynn also says he's been subjected to false accusations.

Washington, D.C. - 1 December 2017

1. Side view, Michael Flynn arriving at side of court house

2. SOUNDBITE (English) Chad Day, The Associated Press:

"So, this morning former national security adviser Michael Flynn appeared with his attorneys here at the Federal District courthouse in Washington and pleaded guilty to a charge of making false statements to FBI agents. Now this plea had been expected, there had been some movements over the last few days that indicated he was making a deal and today Flynn said that in exchange for his plea he is going to cooperate with Special Counsel Robert Mueller as part of his investigation into possible collusion with Trump associates and Russia during the 2016 presidential campaign. One of the main things that came out in the courtroom today and in court papers that were unsealed today is that Flynn has admitted that during December of last year before President Trump came into office, during the transition period, transition officials directed him to make contact with Russian officials about two specific issues. One was the response to U.S. sanctions that were imposed by President Obama in response to Russian election interference. And the other was for a U.N. Security Council resolution. Now, this is the first time that we've actually seen Flynn appear and talk about what happened and some of the things that were being investigated by Special Counsel Robert Mueller and so some of the unanswered questions that we have right now are you know who are these Trump transition officials that were directing his work at that time? And is he possibly cooperating with the government against them or providing information that could be used against them? Today in the courtroom, Flynn appeared and he spoke in a soft voice. He answered several questions that you usually have in these types of hearings. It was a very routine type plea hearing and then shortly after 11:00 today he said those words guilty and pled to this charge. Now this is a felony charge. And so but we don't yet know what this means in terms of whether he'll face any kind of prison time. The maximum for this charge is five years. But, we won't know a lot of that until a later date when they sentence him. "

3. Mid view, front of court house

4. SOUNDBITE (English) Chad Day, The Associated Press:

"So the main unanswered question now is you know coming out of this plea is who's next that Robert Mueller is looking at? You know when you're looking at the plea agreement, there are at least two transition officials that had phone calls with Michael Flynn that he later lied to FBI agents about. And so you know at this point all we know is that they have filed charges against him or a charge against him and that he's pled guilty to that. But there are a lot of indications and as we continue to mine these, these documents that the investigation is moving closer and closer to people in the Trump inner circle."

5. Pan, Flynn departing