Rice said in an interview that Washington "greatly appreciates" the efforts by Britain, France and Germany to try to persuade Tehran to give up its nuclear weapons ambitions.

"What we need with Iran is unity of purpose and unity of message to Iran about what is expected of Iran," she told AFP and the Reuters news agency. "And I frankly think we are getting that."

"Iranians are being told across the board that they cannot be responsible members of the international community and seek nuclear weapons under cover of a civilian nuclear program. That is not acceptable."

Rice sidestepped a question about reported impatience among some of the Europeans who think the United States should be more directly involved in the negotiations. She said Washington has been in close touch.

"We've made clear that we hope for the best, but the Iranians have not demonstrated over time that they have been particularly good about living up to their international obligations," she said.

"The possibility of taking Iran to the (UN) Security Council continues to exist," Rice said. "Our view is that Iran would have to be held accountable for its non-compliance with its international obligations."

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