France, Germany and Britain on Saturday criticized a U.S. decision to end sanction waivers allowing work on Iranian nuclear sites designed to prevent weapon development.

"We deeply regret the U.S. decision to end the three waivers," the three European countries said in a joint statement.

"These projects, endorsed by U.N. Security Council Resolution 2231, serve the non-proliferation interests of all and provide the international community with assurances of the exclusively peaceful and safe nature of Iranian nuclear activities."

The waivers had allowed Russian, Chinese and European companies to work on the conversion of Iran's Arak heavy water reactor, the provision of enriched uranium for a Tehran research reactor and the transfer of spent fuel abroad.

Iran has taken small steps away from its nuclear commitments in a bid to get Washington to remove sanctions as called for by the 2015 accord.

Trump quit the agreement negotiated under his predecessor Barack Obama, under which Iran had drastically curbed its nuclear activities.

But the Trump administration until now had issued waivers to allow companies, primarily from Russia, to keep carrying out the work of the agreement without risking legal ramifications in the world's largest economy.

Iran's U.N. ambassador said that with the end of waivers, U.S. Secretary of State Mike Pompeo was pulling the "final plug" on the nuclear deal two years after Trump withdrew the U.S. from it.

"Claiming US is STILL 'Participant' is not just preposterous; it's FALSE," the envoy Majid Takht Ravanchi tweeted.

The envoy was referring to Washington's claim that it remains a participant in the deal, despite renouncing it, and can push to extend an arms embargo on Iran due to begin expiring in October.