The preliminary U.S. proposal came as a confidential U.N. report described an Iranian initiative that had multiplied Tehran’s stockpile of near-bomb-grade uranium.

The U.N. atomic agency reports that Iran hasn’t cooperated with a nuclear probe, raising the prospect of a snapback of sanctions on Tehran.

The US has sent Iran a proposal for a nuclear deal between Tehran and Washington, the White House confirmed on Saturday. Iranian Foreign Minister Abbas Araghchi said he had been presented with "elements of a US deal" by his Omani counterpart Badr Albusaidi during a short visit to the Iranian capital.