Obama wants to engage Iranian leaders in talks over the country's suspect nuclear program which the U.S. and other western countries worry is aimed at developing nuclear weapons. Iran defends its nuclear program as civilian in nature. EU foreign policy chief Javier Solana said Sunday the bloc would "like very much" to restart nuclear talks with Tehran despite the rising tensions.

Senior White House adviser David Axelrod played down Ahmadinejad's accusations against the U.S., saying they aren't credible and are meant for domestic consumption. "This is political theater," he said on ABC's "This Week."

Iran's supreme leader, Ayatollah Ali Khamenei, called for national unity, appealing to both sides in the dispute, even though he has come down firmly on the side of Ahmadinejad.

"I admonish both sides not to stoke the emotions of the young or pit the people against each other," he said Sunday. "Our people are made of one fabric."

Mousavi, meanwhile, signaled anew he won't drop his political challenge.

In a new statement, he insisted on a repeat of the election and rejected a partial recount being proposed by the government. However, Mousavi's challenge seemed largely aimed at maintaining some role as an opposition figure.

The latest statement by Mousavi, who has been increasingly isolated, appeared Sunday on Ghalamnews, a Web site run by supporters. Mousavi-related Web sites have frequently been blocked by the government, and one was shut down by hackers last week.

For the first time since the election, former President Hashemi Rafsanjani spoke publicly about the unrest, claiming that "suspicious hands" were trying to open rifts between the people and the Islamic system.

He also praised Khamenei for giving the Guardian Council, Iran's top electoral body, more time to evaluate charges of vote-rigging. That was significant because there had been growing speculation that Rafsanjani could be at odds with the supreme leader — setting the stage for a possible high-level power struggle.