(CNN) - Iran's stockpiles of enriched low-grade uranium have exceeded the 300-kilogram limit set in a landmark 2015 nuclear deal, Foreign Minister Javad Zarif said on Monday according to the state-run IRNA news outlet.
The move is thought to be Tehran's first major breach of the accord since US President Donald Trump withdrew from the agreement last year. The deal limited Iran's uranium enrichment in exchange for an easing of international sanctions.
Global nuclear watchdog, the International Atomic Energy Agency, said that its inspectors on the ground in Iran had confirmed the development.
"We can confirm that IAEA Director General Yukiya Amano has informed the Board of Governors that the Agency verified on July 1st that Iran's total enriched uranium stockpile exceeded 300 kg of UF6 enriched up to 3.67% U-235 (or the equivalent in different chemical forms)," IAEA spokesman Fredrik Dahl said in a statement.
Zarif, one of the chief architects of the deal, said later in the day that Iran's stockpiling of more enriched uranium than permitted under the pact did not violate the Joint Comprehensive Plan of Action, or JCPOA, since it reserved the right to respond to Washington's withdrawal from the agreement and subsequent sanctions.
"We have NOT violated the #JCPOA," Zarif said in a post on Twitter, sharing the text of paragraph 36 of the deal, which provides a dispute resolution mechanism when parties believe that other signatories aren't meeting their commitments.
"We gave E3+2 a few weeks while reserving our right. We finally took action after 60 weeks. As soon as E3 abide by their obligations, we'll reverse," Zarif added. The E3 refers to Germany, Britain and France, while the E3+2 also includes Russia and China.
Iran had threatened to surpass the maximum permitted amount of enriched uranium in retaliation to crippling US economic sanctions. During talks in Vienna Friday, European countries still party to the deal made a last-ditch effort to persuade Iran to back off from plans to breach the limit, but it was not enough to dissuade Iranian officials, who believe they haven't done enough to safeguard Tehran from the sanctions.
Foreign Ministry Spokesperson Abbas Mousavi said Tehran's latest moves were reversible.
"We told the Europeans that if more practical, mature and complete measures were taken, Iran's reduction (to its) commitments could be reversed. Otherwise, we will continue," Mousavi said.
Iran said in May that it had quadrupled its production of low enriched uranium. The announcement ratcheted up tensions in the region and set off a series of provocative moves by the US and Iran.
US President Donald Trump responded today with a warning that Iran was "playing with fire." "They know what they're doing. They know what they're playing with. And I think they're playing with fire," he said.
Last week, the US dispatched top-of-the-line F-22 stealth fighters to nearby Qatar. The deployment came a week after an Iranian surface-to-air missile shot down a US drone over the Strait of Hormuz, one of the world's most vital strategic shipping routes.
Iran said the drone was in its airspace, but Washington said it was over international waters.
The US has also blamed Iran for explosions on two oil tankers this month near the strait, as well as on four commercial ships off the coast of the United Arab Emirates last month. Iran has categorically denied responsibility for the ship attacks.
CNN's Sarah El Sirgany, Nada Altaher and Nada Bashir contributed to this report.
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