LONDON, Feb. 3 - Less than a day after President Bush declared he was "working with European allies" to persuade Iran to give up its nuclear program, Secretary of State Condoleezza Rice said the United States would continue to rebuff European requests to participate directly in offering incentives for Iran to drop what is suspected of being a nuclear arms program.

Opening her first overseas trip as secretary, Ms. Rice also declared that the Tehran government´s record on human rights was "something to be loathed" - a harsh comment that comes at a time when many European leaders have asked the United States to help lower tensions with Iran.

"I don´t think anybody thinks that the unelected mullahs who run that regime are a good thing for the Iranian people or for the region," Ms. Rice said to reporters on her plane to London. "I think our European allies agree that the Iranian regime´s human rights behavior and its behavior toward its own population is something to be loathed."

Ms. Rice made her remarks as the Iranians, the Europeans and many in Washington were dissecting Mr. Bush´s comments about Iran - and far gentler words about Saudi Arabia and Egypt - in his State of the Union address on Wednesday night. In the address, Mr. Bush seemed to invite the people of Iran to liberate themselves from their clerical rulers, for the first time matching a specific nation to his Inauguration Day call for an end to tyranny around the world.

But he also sounded willing to support the Europeans in their initiative to negotiate an end to a key part of Iran´s nuclear program.

"Today, Iran remains the world´s primary state sponsor of terror, pursuing nuclear weapons while depriving its people of the freedom they seek and deserve," Mr. Bush said. "We are working with European allies to make clear to the Iranian regime that it must give up its uranium enrichment program and any plutonium reprocessing, and end its support for terror. And to the Iranian people, I say tonight: As you stand for your own liberty, America stands with you."

But he made no effort to urge the people of Egypt or Saudi Arabia to challenge their governments, even though both countries have turned aside Mr. Bush´s past calls that they allow democratic forces to determine who will rule their governments. "The government of Saudi Arabia can demonstrate its leadership in the region by expanding the role of its people in determining their future," he said in the speech, and Egypt "can now show the way toward democracy in the Middle East."

In Washington on Thursday night, a senior administration official said the reason for the difference was simple. "We do not have relations with the government of Iran, and it is not a government moving in the direction of giving its people greater participation in their affairs," the official said. "If anything, they have cracked down on the opposition."

But the official argued that "Egypt and Saudi Arabia are a contrast with Iran, because we do have good relations with those governments, and while they are not perfect they are nonetheless making steps toward greater participation."

The official, who was involved in the decisions leading up to the address, said Mr. Bush "wanted to answer the question asked after his inaugural: What do you do with countries that are allies in the war on terror but need to do more?"

In Iran on Thursday, the country´s supreme leader, Ayatollah Ali Khamenei, predicted that Mr. Bush, like every other American president since Iran´s 1979 revolution, would fail to overthrow the Islamic republic.

"Bush is the fifth U.S. president who wants to destroy the Islamic republic," the ayatollah told university students. "But he will fail as did Jimmy Carter, Reagan, Bush senior and Clinton." Branding the United States "one of the heads of the dragon of world oppression," he charged that Mr. Bush had been installed in the White House by "Zionist and non-Zionist companies and capitalists to serve their interests."

Mohammad Sadegh Kharazi, Iran´s ambassador to Paris, said in an interview on Thursday that Iran should be rewarded, not punished, by the United States for supporting the democratic electoral process in Iraq. "We were the only country in the region to fully support elections in Iraq," Mr. Kharazi said. "And in return we get President Bush´s negative body language. America just doesn´t want to understand our reality. Is it fair? No."

Iran has also made clear, at least in its public statements, that it has no intention of trying to export an Islamic republic to Iraq.

The questions about America´s stance toward Iran coincide with fresh evidence that Iran may be violating the spirit, if not the exact terms, of its Nov. 15 agreement with France, Germany and Britain to temporarily freeze its program to enrich uranium. Enriched uranium can be used to produce energy or, at high enrichment levels, as fuel for nuclear weapons.

Last month, new negotiations began that could give Iran generous rewards on nuclear energy, trade and economic, political and security cooperation if it provides firm guarantees that it is not developing a nuclear weapon.

But the three European countries have uncovered evidence that Iran is doing maintenance work on centrifuge piping at an enrichment plant at Natanz in southern Iran, according to a British official.

The issue is regarded as serious enough that John Sawers, the senior British Foreign Office official involved in the negotiations, protested in meetings in Tehran on Wednesday with Iran´s senior nuclear negotiator, Hassan Rowhani, and Foreign Minister Kamal Kharrazi, a British official said.

The United States also has formally complained to the European negotiators about the issue, in a Jan. 28 letter from John Bolton, the under secretary of state for arms control and international security, the British official said. "We are taking this issue extremely seriously," the official said. "We are reminding Iran of its obligations."

But it is not at all clear that the Iranian action actually violates the accord.

"It´s a bad sign that the first time Iran is supposed to do what it agreed to that it looks as if it is trying to get away with something," said David Albright, president of the Institute for Science and International Security, a nonpartisan arms control group in Washington. "This is something that makes everyone nervous."

Each revelation about Iran´s nuclear program, however mild, is likely to make the Bush administration more hesitant to embrace the European view that the way to curb Iran´s nuclear program is with engagement, not threats.

Mr. Bush has harshly criticized Iran´s clerical rulers and, in the past, even suggested that he favored a change of government. In linking Iran with North Korea and Iraq as an "axis of evil" in his State of the Union address three years ago, he charged that Iran "aggressively pursues" weapons of mass destruction and exports terror "while an unelected few repress the Iranian people´s hope for freedom."

But the administration has left its policy on regime change deliberately ambiguous. While a former deputy secretary of state, Richard L. Armitage, had once said the administration did not favor regime change in Iran, Ms. Rice said on Thursday that "what we support is that the Iranian people should have a chance to determine their own future." She said she hoped her trip would send "a very clear message" that Europe and the United States were united in their approach.

But in tone and substance, her comments suggested that a wide rift remained; Europeans continue to complain that the Bush administration was overly confrontational. Some Europeans fear that the American approach could lead to eventual attacks on areas suspected of being Iranian nuclear sites. The foreign ministers of several European nations have recently begun to warn that without American participation in an incentive package for Iran, their efforts could founder.

"There has to be a sense that there will be a U.S. buy-in to the solution," John Bruton, the European Union´s representative to the United States, told reporters earlier this week, adding that the administration was "not engaged in the way we would like."

But Ms. Rice said Thursday: "It´s not the absence of anybody´s involvement that is keeping the Iranians from knowing what they need to do. They need to live up to their obligations."

Steven R. Weisman reported from London for this article, Elaine Sciolino from Paris and David E. Sanger from Washington. (Copyright 2005 The New York Times Company 02/04/05)