Iranian President Mahmoud Ahmadinejad said Sunday that diplomacy is the only way out of his country's standoff with the West over its disputed nuclear program and insisted he was serious about negotiations.

Iran's leader made the comments a day after asserting that his country would not give up its "nuclear rights," signaling that it would refuse demands to stop enriching uranium or at least not to expand its enrichment work.

An informal deadline expired this weekend on an offer of economic and other incentives by six world powers if Iran agreed to curb uranium enrichment. The United States and its European allies fear Iran intends to use the technology to develop material for nuclear weapons under the cloak of a civilian nuclear power program. Iran denies the accusation.

Ahmadinejad said Saturday that his country's participation in any international talks would "be aimed at reinforcing" what Iran regards as its right under the Nuclear Nonproliferation Treaty to enrich uranium for a civilian power program.

On Sunday, the Iranian leader repeated that his country was "serious in nuclear talks" and hopes "the other side" will be as well.

"In case he hasn't noticed, we are trying to talk with them," White House press secretary Dana Perino said from Kennebunkport, Maine. "The door is open, they just need to step through it by suspending their enrichment of uranium."

Syria's president, Bashar Assad, visited Iran over the weekend but played down any expectations that he could persuade Syria's close ally to meet Western demands.

"I am not mediating and I don't carry any message from any Western country," Assad told reporters before returning to Damascus.

Syria is Iran's closest Arab ally — a legacy of its support for Iran during its war with Iraq in the 1980s — and Assad's visit was his sixth since 2000. He said the visit was a regular one, not for mediating in Iran's nuclear issue. However, he said they discussed the standoff.

Iran's claims that it only wants nuclear technology for the production of energy have failed to quell Western suspicions that it is seeking a pathway to an atomic bomb.

The country was given an informal two-week deadline, set July 19 by the Security Council's permanent members plus Germany, to stop expanding uranium enrichment — at least temporarily — in exchange for their commitment to stop seeking new U.N. sanctions.

The Security Council has imposed three sets of sanctions on Iran over its enrichment and reprocessing of uranium.

U.S. Secretary of State Condoleezza Rice said Saturday that the United States would have no choice "but to begin again to prepare sanctions resolutions for the (U.N.) Security Council" if Iran did not halt the development of its enrichment program.