Iran has declared that it will no longer abide by any of the restrictions imposed by the 2015 nuclear deal.
In a statement, it said it would no longer observe limitations on its capacity for enrichment, the level of enrichment, the stock of enriched material, or research and development.
The announcement followed a meeting of the Iranian cabinet in Tehran.
Tensions have been high over the killing of Iranian General Qasem Soleimani by the US in Baghdad.
Hundreds of thousands turned out in Iran on Sunday to give Soleimani a hero’s welcome ahead of his funeral on Tuesday.
Earlier, Iraqi MPs had passed a non-binding resolution calling for foreign troops to leave the country after the general’s killing in a drone strike at Baghdad airport on Friday.
President Donald Trump has repeatedly threatened that the US will strike back at Iran in the event of retaliation for Soleimani’s death, and said it could do so “perhaps in a disproportionate manner”.
“Iran will continue its nuclear enrichment with no limitations and based on its technical needs,” a statement said.
However, the statement did not say that Iran was actually withdrawing from the agreement and it added that the country would continue to co-operate with the UN’s nuclear watchdog, the IAEA.