The waivers were part of the landmark agreement signed with Tehran in 2015 that sought to limit Iran's nuclear ambitions in return for lifting crippling economic sanctions.

They allowed European, Chinese and Russian companies to work on the conversion of a heavy water reactor in Arak, a major industrial city in western Iran.

"We deeply regret the US decision to end the three waivers covering key JCPOA nuclear projects in Iran," read a joint statement from the three European powers.

"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."

US Secretary of State Mike Pompeo announced the decision to end the waivers earlier this week.

The nuclear deal, known formally as the Joint Comprehensive Plan of Action (JCPOA), was signed by the US, Britain, China, France, Germany and Russia as well as Iran.

However, the US pulled out in 2018 and the latest decision on waivers, following further sanctions, raises the prospect that the agreement could collapse.

Russia has also attacked the decision by Pompeo, with Moscow claiming US foreign policy was becoming "more dangerous and unpredictable".

In Tehran, Iranian foreign ministry spokesman Abbas Mousavi condemned the US decision as a "flagrant violation of Resolution 2231 and the Charter of the United Nations."

He said Iran was ready to "take legal action and act appropriately" if the move harms its nuclear rights, without elaborating.

Iranian Atomic Energy Organisation spokesman Behrouz Kamalvandi said Thursday Washington's "desperate" decision was aimed at distracting attention from its "continued defeats at the hands of Iran".