TEHRAN, Iran -- Iran has begun producing enriched uranium at 60% purity at the country's underground Fordo nuclear plant, official media reported Tuesday, describing it as a response to a resolution by the United Nations' nuclear watchdog.
The increased enrichment, reported by the official news agency IRNA, was seen as a significant addition to the country's nuclear program.
From Vienna, the U.N. nuclear watchdog -- the International Atomic Energy Agency -- said the 60% enrichment at Fordo comes on top of similar production at the Natanz plant in central Iran.
The agency stated Iran plans a "significant expansion" in its production of low-enriched uranium at Fordo and a second production building at Natanz.
Enrichment to 60% purity is one short, technical step away from weapons-grade levels of 90%. Nonproliferation experts have warned in recent months that Iran now has enough 60%-enriched uranium to reprocess into fuel for at least one nuclear bomb.
IRNA did not give details on the amount of the enriched uranium being produced at Fordo.
Later Tuesday, a joint statement from Germany, France and Britain -- the three Western European countries that remain in the Iran nuclear deal -- condemned Iran's latest action to further expand its nuclear program.
"Iran's step is a challenge to the global non-proliferation system," a statement from the three said. "This step, which carries significant proliferation-related risks, has no credible civilian justification."
On Monday, Iran's Foreign Ministry spokesman, Nasser Kanaani, said his country was taking the steps in reaction to a resolution, approved by the International Atomic Energy Agency's board of governors, that called for Iran's cooperation with a probe by the agency into man-made uranium particles found at three undeclared sites in the country.
The joint statement by Germany, France and Britain said Iran's claims that its latest actions are a reaction to that resolution were "unacceptable."
Earlier this month, the IAEA criticized Tehran for continuing to bar the agency's officials from accessing or monitoring Iranian nuclear sites.
It has been nearly two years since energy agency officials have had full access to monitor Iran's nuclear sites, and five months since the surveillance equipment was removed.
The agency's assessment came as efforts to revive Iran's 2015 nuclear deal with world powers, which eased sanctions on Iran in return for curbs on its nuclear program, have stalled.
The United States unilaterally pulled out of the nuclear deal in 2018 under then-President Donald Trump. It reimposed sanctions on Iran, prompting Tehran to start backing away from the deal's terms.
The semi-underground enrichment facility in Natanz is home to thousands of centrifuge machines. Iran began 60% enrichment in Natanz in 2019.