Iran has announced it will break a limit set on uranium enrichment, in breach of the landmark 2015 nuclear deal.
Deputy foreign minister Abbas Araqchi said Iran still wanted to salvage the deal but blamed European countries for failing to live up to their own commitments.
The US unilaterally withdrew from the agreement in 2018.
It has since reimposed strict sanctions on Iran.
The Iranian announcement marks the latest breach of the accord. In May, Iran stepped up its production of enriched uranium, which can be used to make fuel for reactors but also for nuclear weapons.
The country has already stockpiled more enriched uranium than permitted under the terms of the deal.
Speaking at a press conference, Mr Araqshi said Iran would start enriching uranium above a concentration of 3.67% within a few hours, to provide fuel for its Bushehr power plant.
Officials previously said this would mean a concentration of about 5%. Weapons-grade uranium is 90% enriched or more.
Mr Araqchi said Iran will keep reducing its commitment to the 2015 deal every 60 days unless its remaining signatories – China, France, Germany, Russia and the UK – moved to protect it from US sanctions.
The announcement comes a day after French President Emmanuel Macron spoke to Iranian President Hassan Rouhani and expressed his “strong concern” about what would happen if the agreement was abandoned.
Mr Rouhani called on European countries to act now to save the deal.
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