“Iran is not opposed to sending uranium abroad, but is considering how to do that,” Ramin Mehmanparast told a news conference.

He said Tehran wanted a “100 percent guarantee” that it would receive the fuel required for its research reactor and “one of the guarantees is a simultaneous exchange of fuel (exchanging 3.5 percent enriched uranium with 20 percent enriched by world powers) inside the country.”

Iran and world powers have been at loggerheads for weeks, failing to reach a nuclear fuel deal aimed at allaying Western concerns over Tehran’s nuclear programme.

The West, led by Washington, fears Iran might otherwise covertly divert some of its LEU stocks for further enrichment to the much higher levels required for a bomb, an ambition Iranian officials strongly deny.

To defuse the crisis, the UN atomic watchdog brokered a deal last month under which Iran would send 1,200 kilogrammes (2,640 pounds) of LEU, or 70 percent of total stocks, to Russia and then France for conversion into fuel required for the Tehran reactor.

But Iran has rejected that deal amid stiff opposition from its senior officials who oppose sending the LEU in one go. They fear the West might renege on its side of the bargain.