By Dan De Luce

Iran has started expanding uranium enrichment to 60 percent purity at an underground site in Fordow days after foreign governments accused Tehran of failing to cooperate with a U.N. investigation into its past nuclear work.

The decision puts Iran a step closer to having uranium enriched to the weapons-grade threshold of 90 percent and flouts the limits of the 2015 nuclear agreement between Iran and world powers.

The move came amid growing international condemnation of anti-regime protests in Iran, with U.N. human rights officials saying a rising death toll reflected Tehran’s use of lethal force to try to put down the demonstrations.

“Enrichment to near-weapons grade levels using more efficient centrifuges at the deeply buried Fordow site is a serious escalation and raises the risk of a nuclear-armed Iran,” said Kelsey Davenport, director of non-proliferation policy at the Arms Control Association, a Washington-based think tank. Sixty percent enriched uranium “is a hair’s breadth away from the 90 percent level considered weapons grade,” she said. 

The decision will enable Iran “to stockpile uranium enriched to 60 percent more quickly, decreasing the time it would take to produce enough weapons-grade uranium for multiple weapons,” Davenport said.

The director general of the International Atomic Energy Agency, Rafael Mariano Grossi, said in a report on Tuesday to member states that Iran had begun producing highly enriched uranium at 60 percent purity at the Fordow fuel plant, using advanced centrifuges. Iran last year already embarked on enrichment up to 60 percent elsewhere at an above ground site in Natanz.

Iranian state media earlier reported that the government planned to increase uranium enrichment at Fordow to 60 percent for the first time, and that officials had warned it would respond to any reprimand from the IAEA’s board of governors.

Iran’s U.N. mission did not respond to a request for comment.

The 35-nation IAEA board adopted a resolution last week criticizing Iran, demanding Tehran urgently cooperate with the IAEA’s investigation into traces of uranium found at three undeclared sites.

The 2015 nuclear deal between Iran and world powers, known as the Joint Comprehensive Plan of Action, was designed to prevent Iran from developing nuclear weapons. It imposed limits on Iran’s nuclear program in return for an easing of U.S. and international sanctions on Iran. But former President Donald Trump pulled the U.S. from the deal in 2018 and Iran has since blown past the deal’s restrictions, using advanced centrifuges and enriching uranium far beyond a cap of 3.67 percent purity.