Iran will inject uranium gas into 1,044 centrifuges at its underground Fordow nuclear enrichment plant.
Iranian President Hassan Rouhani made the announcement during a speech Tuesday broadcast live on national television, the state-owned PressTV reported.
The centrifuges had been spinning without the gas to produce stable isotopes for industry, agriculture and medicine.
It is Iran’s latest violation of the nuclear deal that it signed in 2015 with the nuclear powers.
Since the Trump administration pulled out of the agreement more than a year ago and reimposed economic sanctions, Iran has begun to arrogate parts of the deal.
China, France, Russia, the United Kingdom, Germany and the European Union remain committed to the pact known as the Joint Comprehensive Plan of Action.
Rouhani reaffirmed that all actions Iran has so far taken to reduce its commitments under the nuclear deal remain reversible.
He said Iran would be willing to restart nuclear talks with the world powers if Washington returns to the deal and removes all the “wrong, cruel and illegal” sanctions it re-imposed on Iran after leaving the deal.
The announcement came a day after Ali Akbar Salehi, head of the Atomic Energy Organization of Iran, announced that Iran is building a prototype centrifuge that is 50 times faster than those allowed under the nuclear deal and is operating 60 IR-6 advanced centrifuges, or double the number Iran was known to have, also in violation of the nuclear deal.