1. US President Barack Obama seated with presidents from Baltic countries in White House Cabinet Room
2. SOUNDBITE: (English) Barack Obama, US President:
"This kind of attack is a challenge to the world. We cannot accept a world where women and children and innocent civilians are gassed on a terrible scale. This kind of attack threatens our national security interests by violating well established international norms against the use of chemical weapons by further threatening friends and allies of ours in the region, like Israel and Turkey, and Jordan and it increases the risk that chemical weapons will be used in the future and fall into the hands of terrorists who might use them against us."
3. Wide of Obama speaking
4. SOUNDBITE: (English) Barack Obama, US President:
"We're not considering any open-ended commitment. We're not considering any boots-on-the-ground approach. What we will do is consider options that meet the narrow concern around chemical weapons, understanding that there's not going to be a solely military solution to the underlying conflict and tragedy that's taking place in Syria. And I will continue to consult closely with Congress. In addition to the release of the unclassified document, we are providing a classified briefing to congressional staff today and we'll offer that same classified briefing to members of Congress as well as our international partners. And I will continue to provide updates to the American people as we get more information."
5. Wide, pull out car carrying US Secretary of State John Kerry leaving White House
6. Pan of CIA (Central Intelligence Agency) Director John Brennan getting into car and leaving White House
7. Joint Chiefs of Staff Chairman General Martin Dempsey
8. SOUNDBITE: (English) Michael Eisenstadt, Director of the Military and Security Studies Program at the Washington Institute for Near East Policy:
"The president really at this point can't not act, both as a result of the fact that originally his red line was crossed and now with all of the leaking that has going on in the media about the preparations for a strike that's been going on, he's pretty far out on a limb and it would be pretty much impossible for him to walk it back at this point, without severe loss of credibility."
9. Detail of White House report on chemical weapons use in Syria
10. Zoom in on map of Damascus
11. SOUNDBITE: (English) Michael Eisenstadt, Director of the Military and Security Studies Program at the Washington Institute for Near East Policy:
"What is remarkable is the fact that President Obama has been very clearly resisting all calls for the United States to get involved in any way in the conflict in Syria and has been doing everything possible to ensure that the US doesn't get involved and to see this turnaround in a very short time is really dramatic."
Edging toward a retaliatory strike, US President Barack Obama said on Friday he was weighing "limited and narrow" action against Syria.
The Obama administration bluntly accused Bashar al-Assad's government of launching a chemical weapons attack that killed at least 1,429 people, far more than previous estimates, including more than 400 children.
Describing the attack as a "challenge to the world," the president said it was a threat to US national security interests.
"We're not considering a boots-on-the-ground approach," Obama said, seeking to reassure a public weary after a decade of war in Iraq and Afghanistan.
Halfway around the world, US warships were in place to deliver a punishing blow.
At the same time, UN personnel carried out a fourth day of inspection as they sought to determine precisely what happened in the attack last week.
The international contingent arranged to depart Syria on Saturday and head to laboratories in Europe with the samples they have collected.
Obama met with his national security aides at the White House and then with diplomats from Baltic countries, saying he had not yet made a final decision on a response to the attack.
But the administration did nothing to discourage the predictions that he would, and soon.
It was an impression heightened both by strongly worded remarks by US Secretary of State John Kerry's remarks and the release of an unclassified intelligence assessment that cited "high confidence" that the Syrian government carried out the attack.
Former US army military analyst Michael Eisenstadt said Obama at this point must act against the Syrian regime.
"The president really at this point can't not act, both as a result of the fact that his red line was crossed," he said.
"It would be pretty much impossible for him to walk it back at this point, without severe loss of credibility."
Obama has long been wary of US military involvement in the struggle, as he has been with turbulent events elsewhere during the so-called Arab Spring.
In this case, reluctance stems in part from a recognition that while Assad has ties to Iran and the terrorist group Hezbollah, the rebels seeking to topple him have connections with al-Qaida groups.
Still, he declared more than a year ago that the use of chemical weapons would amount to a "red line" that Assad should not cross.
Eisenstadt described the turnaround from a president who "has been very clearly resisting all calls for the United States to get involved in any way in the conflict in Syria," to one contemplating military strikes, in a very short time, as "really dramatic."
Obama's efforts to put together an international coalition to support military action have been more down than up.
French President Francois Hollande has endorsed punitive strikes, but British Prime Minister David Cameron's attempt to win a vote of approval in Parliament for military action ended in defeat on Thursday.
American attempts to secure backing at the United Nations have been blocked by Russia, long an ally of Syria.
The Assad government has accused rebels of carrying out the attacks.
The looming confrontation is the latest outgrowth of a civil war in which Assad has tenaciously, and brutally, clung to power.
An estimated 100,000 civilians have been killed in more than two years, many of them as a result of attacks by the Syrian government on its own citizens.