Secretary of State Condoleezza Rice demanded on Thursday that the United Nations take action against Iran's "dangerous defiance" in restarting its nuclear program.

"I don't think it serves anybody's purpose to have a nuclear-armed Iran," Rice said at a briefing in at the State Department.

"I would hope that now seeing the very powerful reaction of the international community that Iran would take a step back and look at the isolation it is about to experience," Rice said.

Rice did not say whether the United States has the votes needed in the U.N. Security Council to punish Iran formally. But Rice added that enough support has been shown for the International Atomic Energy Agency, which oversees nuclear activity, to ask the council to review the issue.

"The council should call for the Iranian regime to step away" from nuclear-weapons development, Rice said at a briefing in Washington. "It is very clear that everyone believes a very important threshold has been cleared."

Rice called for Tehran to end its nuclear program, saying she was "gravely concerned" at "its dangerous defiance of the entire international community."

Iran has claimed its nuclear program was not designed to produce weapons but Rice rejected that, saying, "I don't think anybody believes Iran's protestations that this is a peaceful program."

The Bush administration has urged Iran to resume negotiations with the European Union. Rice said she was hopeful that there is a diplomatic way to resolve the issue and did not discuss specific action that could be taken against Iran.

"We are not yet ready to talk about specific measures" to take against Iran, Rice said. "We have to look hard at how a strong message is sent."

Rice's comments Thursday were unusual as she rarely briefs reporters when she is at the State Department. The Bush administration generally refers comment on the issue to the EU-3, a group of British, French and German officials coordinating discussions with Iran.

The European Foreign Ministers met in Berlin on Thursday and issued a statement urging the U.N. Security Council to take up the matter. They agreed the issue should be referred to the council by the International Atomic Energy Agency.

Asked Thursday whether the U.S. military would take action if Iran fails to act to take out nuclear facilities, Secretary of Defense Donald Rumsfeld declined to answer.

"I don't think my discussing that subject is useful," Rumsfeld said.

Undersecretary of State Nicholas Burns plans to go to Britain, France and Germany next week to coordinate strategy while Undersecretary of State Robert Joseph will travel to Vienna, the headquarters of the U.N. monitoring agency. Burns also will hold talks in India, said a senior U.S. official who spoke on condition of anonymity because the State Department was not ready to issue a formal statement.

The Security Council could try to punish Iran with economic or political sanctions on the grounds it is proceeding secretly to develop nuclear weapons. The immediate objective is to force a resumption of the negotiations and such a plan could backfire if China and Russia want to veto the measures against their ally.

The Council imposed blanket sanctions on Iraq after its 1990 invasion of Kuwait. In the case of Iran, it could start with a demand that Iran negotiate to end its program, and ratchet it up from there.

But plans for Iran are not touching on the approach taken toward Saddam Hussein's Iraq in 2003. "The situations are very, very different," she said.

Iran's president, Mahmoud Ahmadinejad, has vowed to press ahead with a nuclear program that Iran says is designed to produce civilian energy in one of the oil-richest countries in the world.

"Unfortunately, a group of bullies allows itself to deprive nations of their legal and natural rights," he said Wednesday. "I tell those superpowers that, with strength and prudence, Iran will pave the way to achieving peaceful nuclear energy."

By late Thursday, however, it appeared the Iranians had blinked. U.N. Secretary-General Kofi Annan told reporters he had spoken with Iran's top nuclear negotiator. Annan said he was told Iran was eager to get back to the negotiating table with the EU-3.

"They are interested in serious and constructive negotiations but within a timeframe indicating that the last time they did that for two and a half years and no result," Annan said.

While Burns and Joseph will be consulting in Europe, the European Union's foreign minister, Javier Solana, plans to be in Washington to coordinate with Bush administration officials.

FOX News' Teri Schultz and Bret Baier and The Associated Press contributed to this report.