Secretary of State Condoleezza Rice signaled Thursday that time is running out for Iran to avoid being hauled before the U.N. Security Council over its disputed nuclear program, and she denied that the threat is mere "saber rattling."

Rice avoided declaring an end to negotiations between Tehran and European nations aimed at averting punishment at the powerful United Nations body. Her skepticism about progress in the talks was clear, however, and she chose unusually blunt language to lay out the probable next step.

"When it's clear that negotiations are exhausted, we have the votes" to take Iran before the Security Council for possible punishment, Rice told reporters. "There is a resolution sitting there for referral. We'll vote it."

The United States accuses Iran of using a program to develop nuclear power plants as a way of disguising ambitions to build nuclear weapons. Iran denies the accusation and has recently threatened to resume some nuclear research that was suspended during talks with the Europeans.

The United States is not a party to the talks, but is supporting European efforts to divert Iran from pursuing technology that could be used for bomb-making. The U.S. has no diplomatic relations with the nation that stormed the U.S. Embassy in Tehran in 1979 and held Americans hostage for more than a year.

Rice said world opinion is now almost universally arrayed against Iran's nuclear position, and she implied that the United States and its allies hold the cards.

"We've carefully built a consensus" about the dangers of a nuclear Iran and what to do about it, Rice said. "That's not saber rattling, that's diplomacy ... and diplomacy includes what you do in the Security Council."

Iran reneged Thursday on a pledge to provide the head of the U.N. nuclear watchdog agency with details of its plans to move toward uranium enrichment, failing to send representatives as promised for discussions on the program.