Diplomats are concerned about an intelligence report that says Iran is trying to import 1,350 tons of purified uranium ore from Kazakhstan in violation of United Nations Security Council sanctions.
Such a deal would be significant because Tehran appears to be running out of that material, which it needs to feed its uranium enrichment program.
A summary of the report obtained by The Associated Press on Tuesday said the deal could be completed within weeks. It said Tehran was willing to pay $450 million for the shipment.
An official from the country that drew up the report said Kazakh government employees acting on their own were behind the deal. The official demanded anonymity in exchange for discussing intelligence matters.
After-hours calls put in to offices of Kazatomprom, the Kazak state uranium company, in Kazakhstan and Moscow, were not answered. There was no immediate reaction from Tehran.
Iran is under three sets of Security Council sanctions for refusing to freeze its enrichment program and related activities that could be used to make nuclear weapons. Tehran denies such aspirations.