Hundreds of Iranians living in Washington staged a rally in front of the White House on Sunday.
They denounced the ongoing repression of the students' movement at Tehran University.
They also called on the United States for a change in its policy of appeasement towards Iranian President Mohammed Khatami.
About a hundred Iranians gathered in front of the White House on Sunday in support of the thousands of Iranian students who staged a fourth day of protests in Tehran on Sunday.
Demonstrators in Washington chanted slogans against Mohammed Khatami, the reformist President of Iran.
They accused Khatami of portraying himself as a reformist to the outside world while being a pawn of hard-line supreme leader Ayatollah Ali Khamenei.
The U-S were also criticised for their soft line towards the Iranian government.
"Iranian people are coming here to say that the appeasing policies of the United States, policy makers here, their appeasing policies towards Khatami and the present regime in Iran is giving an open hand to the government in Iran to do such suppressive and brutal attacks on Iranian students, right now as you see it on camera everywhere. Just a simple demonstration has turned into such a suppressive attitude of the government".
SUPER CAPTION: Soona Samsami, US representative of national congress of resistance of Iran
The student uprising in Tehran was triggered by a violent and unauthorised police raid on Friday on a Tehran University dormitory.
Police and hard-line activists stormed the dormitory after a small demonstration by reformist students supporting press freedom.
After the raid, 20 people were believed to have been hospitalised and hundreds of students arrested.
Since Friday, students started calling for the resignation of powerful hard-liners in the Islamic government, who allegedly backed the violent raid.
They have also been demanding the resignation of Iran's hardline police chief, who reports to the country's dominant clergy.
And Iran's government announced on Sunday it fired two security chiefs responsible for the raid and acknowledged that one person had been killed during the violence.
With the crowds at Tehran University estimated to have soared to ten thousand, their Iranian colleagues living in Washington believe these are the first steps towards a revolution.
"They are students, they are people. Governments are always changed by people. If you look at any revolution, it starts from universities and then it gets to the people. And then it's the people that make that revolution. And any revolution has a cost and unfortunately so far this movement that they have started has cost some people's lives.
SUPER CAPTION: Borna Safa, student
Meanwhile in Iran, protests were reported to have spread to major cities around the country.
I-R-N-A, the official Islamic Republic News Agency, reported that several people were injured in clashes between moderate and hard-line students.
And, in a sign that the government was losing patience with the demonstrations, Tehran radio broadcast a statement by the authorities against further protests.
Security forces warned they would prevent protests by those who lacked permission from the Interior Ministry.
Iranian students in Washington call this repression.
"Obviously it makes me feel very angry. My people are getting killed. If anybody dares to speak their minds or even dares to say anything against the government, they are suppressing them so much. Things like this always happen. people are always killed, there's always torture going on, there's executions going on. In the past three days alone just six or seven students have been killed because they dared to express an opinion or any kind of thought against the government.
SUPER CAPTION: Zahra Zargar, student
Rallies similar to the one in Washington also took place in Los Angeles, Berkeley, New York, Houston and four cities in Canada.
Ayatollah Ali Khamenei, Iran's supreme leader, now faces his most serious battle in a power struggle against allies of Iran's reformist President Mohamad Khatami.
The crux of the power struggle between hard-liners and reformists is over the limited powers of the elected president.
Khamenei, who leads the hard-liners, controls the armed forces, police, judiciary, the Intelligence Ministry and the radio and television networks. But he is not elected.
Khamenei has previously managed to stand above criticism, but cries of "Khamenei must quit" in the past four days have broken that taboo.
The protests have been a wake-up call for hard-liners who have spent recent months closing down moderate newspapers and arresting Khatami allies.