The UK, France and Germany on Sunday rejected a unilateral declaration of UN sanctions on Iran by the US and said Washington had no authority to initiate the snapback because it was no longer a party to the 2015 nuclear deal with Tehran.
The UK, France and Germany, known as the E3 powers, said the US withdrew from the accord in May 2018 and therefore the declaration from the Trump administration "is incapable of having legal effect".
US Secretary of State Mike Pompeo said on Saturday that UN sanctions on Iran were back in force and promised to punish anyone who breached them.
Mr Pompeo last month accused the E3 of “siding with the ayatollahs” for condemning the move when the US initiated the snapback process.
Europe's major players have continued to back an accord that was supposed to limit Iran's nuclear abilities.
"The E3 remains committed to fully implementing UNSCR 2231 (2015) by which the JCPOA was endorsed in 2015," said the British, French and German foreign ministers.
“We have worked tirelessly to preserve the nuclear agreement and remain committed to do so.”
Last week UK Foreign Secretary Dominic Raab said he shared US concerns about Iran's nuclear and regional threat, and admitted that the nuclear accordneeded changes.
“I think the UK’s position on the JCPOA is well known and the reasons for that are well known. But we’ve always welcomed US and indeed other efforts to broaden it,” he said after talks with Mr Pompeo in Washington.
“We don’t think the JCPOA is perfect by any stretch of the imagination. It should be broadened.
"Our ambition for a broader rapprochement, a more comprehensive deal, is I think in exactly the same place as the US.”
