Secretary of State Condoleezza Rice Friday urged more international pressure on Iran to halt its nuclear program, or face possible action by the U.N. Security Council. The situation is expected to be a major issue in talks Ms. Rice will hold next week in New York on the sidelines of U.N. meetings.

The Bush administration has contended that Iran has a secret nuclear weapons program, and it has supported a referral of the issue to the U.N. Security Council.

But officials here have acknowledged that such a move would lack credibility, unless there were broad support among council members for sanctions by the Security Council against Tehran.

At a news briefing here, in advance of next week's world summit and other U.N. events, Ms. Rice made an unusual public appeal for influential countries to join the United States and the European Union in exerting political pressure on Iran.

The Secretary said Iran's walkout from long-running nuclear talks with Britain, France and Germany, and its resumption of some uranium refining activity is unacceptable and that the message to Tehran to that effect needs to be broad-based. "Iran needs to get a message from the international community that is a unified message. By this, I mean, not just the E.U.-Three and the United States, but also Russia and China and India, and others, that it is not acceptable for Iran to enter into negotiations that are aimed at restoring confidence that they are going to live up to their international obligations, and then, summarily walkout out of them and break the agreement," she said.

Ms. Rice said Iran's refusal to return to the suspension of sensitive nuclear activities, as prescribed in its November 2004 Paris agreement with the E.U.-Three, leaves the international community with few choices other than a Security Council referral.

Ms. Rice will have bilateral meetings in New York with foreign ministers from several countries considered pivotal on the nuclear issue, and she will join President Bush back in Washington late next week for talks with Russian President Vladimir Putin.

The Russian government, which is building a nuclear power plant for Iran, has repeatedly said it opposes reporting Iran to the Security Council.

Ms. Rice will not be meeting with Iranian President Mahmoud Ahmadinejad, who will be among world leaders in New York, though she said under questioning she would greet him if they encountered each other at a U.N. event.

The Bush administration announced earlier this week it had given Mr. Ahmadinejad a visa, in keeping with its obligations as the United Nations host country, this in spite of charges that, as an Iranian student leader in 1979, he may have taken part in the takeover of the U.S. Embassy in Tehran.

Ms. Rice declined to discuss details on an inter-agency U.S. investigation that was said to have found Mr. Ahmadinejad technically ineligible for a visa, under standard rules.

She would say only that there are continuing concerns about the Iranian president's past, which the Tehran government should clear up.