Major powers meet today to discuss fresh sanctions against Iran to curb its nuclear activities.
Officials from Britain, China, France, Russia, the United States, and Germany will gather in New York.
They will assess Tehran's response to their offer in October to exchange uranium for nuclear fuel.
Iran's Foreign Minister Manochehr Mottaki has said Iran accepts the offer "in principle," but with reservations.
U.S. Secretary of State Hillary Clinton said this week the Obama administration thinks the best way to pressure Iran is to impose new sanctions aimed at the country's ruling elite.
But analysts say China and Russia are sceptical of new sanctions and the White House has said China will be sending a lower-level official to today's talks.
China's UN ambassador has said it is too early to consider new sanctions.
The UN Security Council, including China, has previously called for Iran to stop enriching uranium and has issued three sets of sanctions.