American officials said it was unclear whether Iran’s declaration to Dr. ElBaradei was its final position, or whether it was seeking to renegotiate the deal  a step the Americans said they would not take.

Michael Hammer, a spokesman for the National Security Council, said that “we await clarification of Iran’s response,” but that the United States was “unified with our Russian and French partners” in support of the agreement reached in Vienna. That agreement explicitly called for Iran to ship 2,600 pounds of low-enriched uranium to Russia by Jan. 15, according to officials who have seen the document, which has never been made public.

News of the accord led to a political uproar in Iran, with some leading politicians arguing that the West could not be trusted to return Iran’s uranium, produced at the Natanz nuclear enrichment plant. Clearly, however, the Iranian government does not want to appear to be rejecting the agreement. Mr. Ahmadinejad, in a speech in the northeastern city of Mashhad that was broadcast live on state television on Thursday, said, “We welcome cooperation on nuclear fuel, power plants and technology, and we are ready to cooperate.”

He did not address Iran’s efforts to change the deal, but cast it as a victory for Iranian steadfastness against the West. “A few years ago, they said we had to completely stop all our nuclear activities,” Mr. Ahmadinejad said. “Now, look where we are today. Now, they want nuclear cooperation with the Iranian nation.”

In fact, the Iranians found something to like in the Vienna deal. It essentially acknowledged their right to use low-enriched uranium that Iran produced in violation of three Security Council agreements. The Obama administration and its allies were willing to create that precedent because the material would be returned to Iran in the form of fuel rods, usable in a civilian nuclear plant but very difficult to convert to weapons use.

Mr. Ahmadinejad’s remarks seemed to extend Iran’s two-track public position on the nuclear dispute, offering a degree of compliance while also insisting that there were limits to its readiness for cooperation.

“As long as this government is in power, it will not retreat one iota on the undeniable rights of the Iranian nation,” Mr. Ahmadinejad said. “Fortunately, the conditions for international nuclear cooperation have been met. We are currently moving in the right direction and we have no fear of legal cooperation, under which all of Iran’s national rights will be preserved, and we will continue our work.”