Ms Rice said a "tremendous coalition" of nations was united in saying that Iran had a right to a peaceful nuclear energy programme, but not technologies that could lead to nuclear weapons.
She was speaking as a British think-tank warned US air attacks on Iranian nuclear and military facilities were likely to kill thousands of people, cause a long-lasting war, and push Iran to accelerate its atomic programme.
But Ms Rice was keeping up the pressure on Iran.
"They've been lying to the international community for 18 years," she said. "The Iranians now need to step back, look at where they are, see that they're isolated ... and get back into negotiations."
Asked about reports that the US was making plans for a possible military strike, Ms Rice said the US was dedicated to a diplomatic solution, but the "president never takes any options off the table".
However, the Oxford Research Group said military action against Iran, "by the United States or Israel, should not be considered under any circumstances".