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The US says it is ready to follow up with Iran on an aborted plan to provide fuel for a nuclear research reactor.
A US State Department spokesman made the announcement on Wednesday. The initial proposal was put forward in Geneva last October, during discussions between Iran and the five permanent UN Security Council members plus Germany.
Under the proposed deal, Iran would send low-enriched uranium to Russia and France for further purification. It would then be sent back to a reactor in Tehran that makes medical isotopes.
The six major powers fear Iran is using its uranium enrichment program as a cover to develop nuclear weapons. Tehran denies any such plans.