"There is no new proposal on the table," White House spokesman Mike Hammer said, responding to claims from the head of Iran's atomic energy organization, Ali Akbar Salehi.
Salehi told news agencies that France, Russia and the United States had made the offer in response to Tehran's announcement last week that it had begun enriching uranium to a higher 20 percent level.
But Hammer, a spokesman for the White House's National Security Council, dismissed the claim and urged Iran to work with the UN's International Atomic Energy Agency (IAEA) on an existing proposal aimed at defusing the crisis.
Under the proposal drafted by the UN watchdog and backed by the major powers, Iran would ship out most of its stocks of low enriched uranium in return for receiving fuel for the Tehran reactor from France and Russia.
"The door remains open for Iran to accept the practical, fair, and responsible proposal put forth by the IAEA last fall that would enable Iran to meet its medical humanitarian needs as well as build international confidence in Iranian intentions," said Hammer.
"Iran should engage directly with the IAEA."
