European powers have triggered a dispute mechanism over the nuclear deal with Iran, after the country took a further step back from its commitments.
Iran has suspended all limits on its production of enriched uranium, which can be used to make reactor fuel but also nuclear weapons.
It has said it is responding to sanctions reinstated by the US when it withdrew from the accord in 2018.
The nuclear deal saw Iran, which insists its nuclear programme is entirely peaceful, agree to limit its sensitive activities and allow in inspectors in return for the lifting of crippling economic sanctions.
US President Donald Trump reinstated them to force Iran to negotiate a new agreement that would place indefinite curbs on its nuclear programme and also halt its development of ballistic missiles. But Iran has so far refused.
The other parties to the deal – the three European powers plus China and Russia – have tried to keep it alive. But the sanctions have caused Iran’s oil exports to collapse and the value of its currency to plummet, and sent its inflation rate soaring.