The Iranian Foreign Minister says he has spoken by phone with the director of the U.N.'s nuclear watchdog agency after a report from the agency said Iran is further increasing its stockpile of uranium enriched to near weapons-grade levels.

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.

An IAEA report revealed that Iran has increased its stockpile of uranium enriched up to 60% purity, close to weapons-grade levels of 90%.