WASHINGTON -- The Obama administration will leave open the door for discussions with Iran over its nuclear ambitions even as demonstrators question the legitimacy of President Mahmoud Ahmadinejad's re-election, administration officials said Sunday.

Ahmadinejad has accused the West of stoking unrest, singling out Britain and the United States for alleged meddling. Last week, Iran expelled two British diplomats, and Britain responded in kind. Iran has said it's considering downgrading diplomatic ties with Britain.

The U.S. has not had diplomatic relations with Tehran since the aftermath of the Iranian revolution in 1979. On Saturday, Ahmadinejad said he would make the U.S. regret its criticism of the postelection crackdown and said the "mask has been removed" from Obama's efforts to improve relations.

Susan Rice, the U.S. ambassador to the United Nations, said Sunday that Ahmadinejad is falling back on his government's usual strategy of blaming the West and the U.S. in particular for its internal problems.

"This is a profound moment of change. And what Ahmadinejad says to try to change the subject is, frankly, not going to work in the current context, because the people understand that the United States has not been meddling in their internal affairs," she said.

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The legitimacy of the government, while questioned by the people of Iran, is not the critical issue for the U.S. goal of preventing Iran from developing a nuclear weapons capability, Rice said.

"It's in the United States' national interest to make sure that we have employed all elements at our disposal, including diplomacy, to prevent Iran from achieving that nuclear capacity," she said.

Both Rice and David Axelrod, Obama's top adviser, said Ahmadinejad doesn't appear to have the final say over Iran's foreign policy. Axelrod, dismissing Ahmadinejad's harsh language against the U.S. and Obama as "bloviations," said being open to talks with Iran is not an effort to reward the country.

"We are looking to ... sit down and talk to the Iranians and offer them two paths. And one brings them back into the community of nations, and the other has some very stark consequences," Axelrod said.

"We are also mindful of the fact that the nuclear weapons in Iran and the nuclearization of that whole region is a threat to that country, all countries in the region, and the world. And we have to address that. We can't let that lie," he said.

Axelrod said Tehran faces a choice between engaging the West or facing further isolation in the wake of a presidential election that sent protesters to the streets raising questions about its validity.

"Let's be clear that we didn't meddle in the election in Iran," he said. "The dispute in Iran is between the leadership in Iran and their own people, and plainly, Mr. Ahmadinejad thinks that by fingering the United States, that he can create a political diversion. So I'm not going to entertain his bloviations that are politically motivated."

Rice said the protests signal a profound moment of change in Iran and that the consequences of the protests have yet to unfold.

"Something extraordinary has happened of late in Iran, and the popular discontent, the incredible diversity of the coalition that has come together to demand change, from women to the elderly to youth, the very religious to the more secular, has been quite extraordinary," she said.

Rice appeared on CBS television's "Face the Nation" and Axelrod on both ABC's "This Week" and NBC's "Meet the Press."