Iran is to lift all limits on its development of centrifuges used to enrich uranium on Friday — the latest step in reducing its commitments under a 2015 nuclear deal with world powers.
President Hassan Rouhani said the country would do whatever was necessary to be able to accelerate enrichment.
Enriched uranium can be used to make reactor fuel but also nuclear weapons.
Iran stopped abiding by two commitments in July in response to sanctions the US reinstated when it abandoned the deal.
President Donald Trump wants 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.