The UN nuclear watchdog said there were inspectors on the ground in Iran after the country's spokesperson claimed it had begun injecting uranium gas into advanced centrifuges in violation of its 2015 nuclear deal with world powers.
Behrouz Kamalvandi of the Atomic Energy Organisation of Iran made the announcement in a news conference surrounded by advanced centrifuges as he warned Europe had little time left to save the deal.
This is not the first time Iran has breached the stockpile and enrichment level limits set by the deal.
Iran claimed it could revert back to the terms of the accord if Europe delivered the sanctions relief promised in return for curbing Tehran’s nuclear programme.
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.
“Our stockpile is quickly increasing, we hope they will come to their senses,” Mr Kamalvandi 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.