Rice complained that Britain, France and Germany had failed to make sufficiently clear the threat of UN sanctions if Tehran refused to renounce its suspected nuclear weapons ambitions.

"The Iranians need to hear that if they are unwilling to take the deal, really, that the Europeans are giving ... then the Security Council referral looms," Rice said in an interview with Fox News. "I don't know that anyone has said that as clearly as they should to the Iranians," she said.

The negotiations over Iran's suspected nuclear ambitions have been a major issue throughout Rice's week-long tour of Europe and the Middle East, her first trip since becoming chief US diplomat last month. She did say Washington has "no deadline" for progress in diplomatic efforts to secure guarantees from Iran over its suspected nuclear arms program.

The United States accuses Iran of trying to obtain nuclear weapons under cover of developing a civilian atomic energy program, and has not excluded a military option against Tehran. Washington has so far supported the three EU countries' diplomatic efforts, which have focused on getting Iran to promise not to make the bomb in return for trade privileges with the 25-nation bloc.

Getting tougher

"The international community has got to be certain to speak with one very tough voice to the Iranians that it is not going to be acceptable for Iran to build a nuclear weapon under cover of civilian nuclear power," Rice told Fox. She said the United States had believed all along the Iranians should be referred to the UN Security Council for alleged violations of international non-proliferation norms.

"They need to hear that the discussions that they're in with the Europeans are not going to be a kind of way-station where they are allowed to continue their activities, that there's going to be an end to this and that they're going to end up in the Security Council," Rice said.

Her remarks come a day after Rice flew to Paris, a hotbed of opposition to the US-led invasion of Iraq, proclaiming a "new chapter" had been opened in transatlantic relations strained for two years by divisions over the war.

At the same time, French Foreign Minister Michel Barnier said the Europeans needed more support from the United States if they were to persuade Tehran to renounce its suspected attempts to develop a nuclear bomb. "We need the confidence and the support of the United States in this very delicate phase we are in. And that's what the message is that we conveyed to Condi Rice," Barnier said.

No direct talks

But Rice shrugged off a suggestion that Washington and Tehran have direct talks to resolve the nuclear issue. "Everybody knows what the Iranians need to do," she told reporters in Paris. "They just need to do it.

At their latest round of talks with Iran in Geneva Tuesday, according to diplomats, Britain, France and Germany warned the country about activities that verge on breaches of its deal to freeze nuclear fuel cycle work.

Rice flew into Brussels Wednesday for a working lunch with her NATO counterparts and talks with European Union officials before heading off for Luxembourg, the last stop on her tour of eight European nations.