Iran has begun injecting uranium gas into advanced centrifuges in violation of its 2015 nuclear deal with world powers, a spokesman said.
Behrouz Kamalvandi of the Atomic Energy Organisation of Iran made the remarks in a news conference carried on live television.
He spoke from a podium with advanced centrifuges standing next to him.
Iran already has breached the stockpile and enrichment level limits set by the deal, while stressing it could quickly revert back to the terms of the accord, if Europe delivers the sanctions relief promised in return for curbing Tehran’s nuclear programme.
Mr Kamalvandi warned that Europe had little time left to save the deal.
President Donald Trump withdrew America from the accord over a year ago before imposing crippling trade sanctions on Iran.
“As far as the other side does not implement their commitments, they should not expect Iran to fulfil its commitments,” Mr Kamalvandi said.
Mr Kamalvandi said Iran had the ability to go beyond 20% enrichment of uranium.
Analysts say 20% is just a short technical step away from 90% enrichment, which is weapons-grade level.
Mr Kamalvandi warned several times in his comments that Iran was rapidly approaching a point that would mean a full withdrawal from the deal.
“Our stockpile is quickly increasing, we hope they will come to their senses,” he said.
However, he stressed that Iran would allow UN inspectors to continue to monitor sites in the country.
A top official from the UN’s International Atomic Energy Agency was expected to meet with Iranian officials in Tehran on Sunday.