Johnson on Tuesday emphasised the British government's commitment to the landmark 2015 deal that has been hanging by a thread since US President Donald Trump's 2018 withdrawal from the hard-won multilateral agreement.

His proposal for a "Trump deal" came on a day when Britain, France and Germany triggered a dispute mechanism against Iran for violating the accord that gave Iran relief from sanctions in return for curbs on its nuclear programme.

But the Iranian president dismissed the idea of replacing the Joint Comprehensive Plan of Action, or JCPOA, with an accord the British premier called "the Trump deal".

"I don't know what the prime minister in London was thinking when he was saying to put aside the JCPOA and implement the 'Trump deal'," Rouhani said.

"Trump has done nothing but violate international covenants and laws," he said in televised remarks after a cabinet meeting, citing the 2017 Paris climate pact and a June 2018 agreement on the UN Human Rights Council.

Since Trump withdrew from the JCPOA and began reimposing sanctions, Tehran has retaliated by winding down its commitments to the nuclear accord.

On Tuesday, the three European parties to the deal triggered a provision intended to hold Iran to account.

Britain, France and Germany all emphasised that despite this action, they remained committed to the agreement.

But Tehran warned the three countries of unspecified "consequences" for any "abuse" of the dispute mechanism.