U.S., allies set demands as Iran nuclear talks loom

REUTERS -- The United States and its allies will demand that Iran halt higher-grade uranium enrichment and immediately close an underground nuclear facility at a new round of talks this week over Tehran's nuclear standoff with the West, a senior U.S. official said.

The negotiations between Iran and world powers - a resumption of talks that collapsed more than a year ago - will be held on April 14 in Istanbul, a spokesman for EU foreign policy chief Catherine Ashton said.

The Obama administration sought to define the parameters for the much-anticipated meeting, which it has said could represent Tehran's last chance to resolve the nuclear dispute diplomatically.

A senior U.S. official said on Sunday that one of the "near-term priorities" would be to get Iran to agree to immediately shut its recently completed Fordow facility, built under a mountain near the Shi'ite Muslim holy city of Qom.

The New York Times reported that negotiators for the West would press Iran to ultimately dismantle the site, which is reported to have been used to expand uranium enrichment.

Another key opening demand from Washington and its allies will be for Iran to stop production altogether of 20 percent enriched uranium, the administration official said.

Nuclear bombs require uranium enriched to 90 percent, but much of the effort required to get there is already achieved once it reaches 20 percent purity, shortening the time needed for any nuclear weapons "break-out".

Iran has remained defiant, saying its program is for power generation and producing isotopes for medical purposes, not for bomb-making.

But the U.N. Security Council has demanded a full suspension of enrichment, both to the 20 percent and the 3.5 percent level, and Washington has made clear that its broader goal is to make sure that Iran abides by those requirements.

"Our position is clear: Iran must live up to its international obligations, including full suspension of uranium enrichment as required by multiple U.N. Security Council resolutions," said Tommy Vietor, spokesman for the White House National Security Council.

President Barack Obama is under pressure at home to take a tough line with Iran as he seeks re-election in November.

Republican presidential candidates have accused him of not being hard enough on Iran, even as he has spearheaded international sanctions that are taking a toll on the Iranian economy and its vital oil sector.

He has pressed U.S. ally Israel to hold off on any pre-emptive attack on Iran's nuclear sites to give sanctions and diplomacy more time to work. But he has also declared that military action remains an option as a last resort.