The president has been choosing his words carefully, calibrating his response as events unfold in Iran.
His comments on the right of dissent and peaceful protest have grown stronger over the last few days. But there has been no change in his view that the Iranian people must choose their own leaders, without any outside interference.
In his latest statement, issued Saturday, Mr. Obama called the Iranian government's crackdown on protesters violent and unjust. And he warned once again that the world is watching what is happening in Tehran.
Some leading Republicans in the U.S. Congress are urging the president to do more.
Senator John McCain, Mr. Obama's opponent in the 2008 U.S. presidential election, told the CBS television program Face the Nation the White House must exert - what he called - moral leadership.
"I don't consider it meddling when you stand on the side of the principles that made our nation the greatest nation in history," he said.
On ABC's This Week, Republican Senator Lindsey Graham said the president's initial response was timid and passive.
"The young men and women taking to the streets in Tehran need our support. The signs are in English. They are basically asking for us to speak up on their behalf," he said.
But there are divisions in the Republican ranks. Former Secretary of State Henry Kissinger, for example, has said President Obama has taken the right approach.
Mr. Obama is also getting support, as expected, from senior congressional Democrats. They agree that the United States should not give the Iranian government cause to label the protesters pawns of America. Iranian leaders have accused the United States and Britain of meddling.
Senator Christopher Dodd says the president is striking the correct balance. Dodd also appeared on ABC's This Week.
"The worst thing that we could do at this moment for these reformers, these protesters, these courageous people in Tehran, is allow the government there to claim this is a U.S.-led opposition," he said.
One of the leading voices in the U.S. Senate on Iran - Democrat Evan Bayh - told the Fox News Sunday television program that the Iranian government is losing legitimacy at home. He said Iran's leaders want to shift the focus elsewhere.
"We should not let them change the narrative to one of meddling Americans, American and western imperialism and that sort of thing, because, historically, that sort of narrative has resonated, and we might allow them to change the subject within Iran and within the rest of the Islamic world. Let's not let them do that," he said.
Bayh said the demonstrations in Iran are now about far more than a disputed election. He said the protesters are seeking a better future for themselves and their country.