Iran has turned all of its enriched uranium closest to the level needed to make nuclear arms into more harmless forms, the United Nations' nuclear agency has said.
Tehran had committed to convert or dilute its 20-percent enriched stockpile under an agreement with six powers last November that froze its atomic programmes pending negotiations on a comprehensive deal. Those talks were extended on Saturday to November 24.
The development was noteworthy in reflecting Iran's desire to continue the diplomatic process with the six countries - the United States, Russia, China, Britain, France, and Germany.
Iran had more than 200kg of 20 percent enriched uranium when the preliminary agreement was reached. That's nearly enough for one warhead.
A report from the UN's International Atomic Energy Agency said that all has now been converted or diluted, AP news agency reported. The report said Iran was observing all of its other commitments as well.
At 20 percent, enriched uranium can be converted quickly to arm a nuclear weapon. Iran denies wanting such arms.
Tehran is keen to seal a deal that would end nuclear-related sanctions on its economy, but is resisting a US-led drive to put stiff, long-term constraints on atomic activities that have both peaceful and weapons-related applications.
The main dispute is over uranium enrichment, which can make both reactor fuel and the fissile core of nuclear warheads.
Up to last week Tehran had demanded that it be allowed to expand its enrichment programme over the next eight years to a level that would need about 190,000 current-model enriching centrifuges.
It now has about 20,000 centrifuges, with half of them operating. Iranian officials have recently signalled they are ready to freeze that number for now. But US Secretary of State John Kerry said last week it was "crystal clear" that even 10,000 are too many.
Diplomats say Washington wants no more than 2,000 of the machines.