U.S. Secretary of State Hillary Clinton has called on Iran to be prepared to "take concrete steps," particularly in halting uranium enrichment to 20 percent, at the next round of talks with world powers.
Enriching uranium to 20 percent purity brings it closer to becoming material that could be used in a nuclear bomb.
Iran has so far ruled out halting 20 percent enrichment, saying it needs the material for medical purposes and is not making a nuclear weapon.
Clinton, speaking in Istanbul on June 7, said the 20 percent issue will be a key demand of Western states, who suspect Iran of having a nuclear weapons program, during talks on June 18-19 in Moscow.
The talks will bring together Iran with Britain, China, France, Germany, Russia, and the United States.
Based on reporting by Reuters