More than 500 parliamentarians from Franceinfo-icon, Germanyinfo-icon and the UKinfo-icon have written to their USinfo-icon counterparts urging them to persuade Donald Trumpinfo-icon not to abandon the Iraninfo-icon nuclear deal.

In a joint statement published in the Guardian, Der Spiegel, the New York Times and Le Monde, they urged a White House rethink before the 12 May deadline set by Trump to pull out of the deal, known as the joint comprehensive plan of action (JCPOA), unless Europe can come up with a new policy that will meet his concerns.

"The US government threatens to abandon the JCPOA, although Iran fulfils its obligations under the agreement," the letter said. They warn that "an exit from the US would have fatal consequences".

France, Germany and the UK negotiated the landmark deal in 2015 that lifted sanctions on Iran in exchange for strict limits on its nuclear programme, and are using all their leverage to try to persuade Trump that the deal is salvageable.

"The short-term impact of this move would put an end to Iran's nuclear programme controls, which could provide a new source of devastating conflictinfo-icon in the Middle Eastinfo-icon and beyond," it said.

But it said even more serious were the long-term risks: damage to the credibility of the signatories as partners in international negotiations and more generally to diplomacy as a tool to secure lasting peace and security.

"Leaving the agreement would diminish the value of all the promises and threats our countries make," the parliamentarians said.

They added that if the deal broke down it would be nigh on impossible to assemble another grand coalition built around sanctions against Iran.

Trump is concerned by an Iranian ballistic missileinfo-icon programme, the speed with which Iran could obtain a nuclear capability at the end of the 10-year deal and more broadly Iran's interventionist stance around the Middle East - notably in Yemeninfo-icon, Lebanoninfo-icon and Syriainfo-icon.The campaign was organised by the German Green MP Omid Nouripour, the French MP Delphine O of Emmanuel Macron's En Marche! movement, and the British Conservative MP Richard Bacon.

Prominent signatories from Germany include the Green party leader, Annalena Baerbock, the leftwing politician Gregor Gysi, the FDP parliamentary group vice-president, Alexander Graf Lambsdorff, and the Bundestag vice-presidents Thomas Oppermann (SPD) and Claudia Roth (Green). There were no signatories from the CDU.In an attempt to mollify the White House, the governments in Berlin, Parisinfo-icon and London have been pushing for sanctions against Iran to be stepped up rather than for the cancelling of the deal. And the letter's signatories criticised Tehraninfo-icon's "aggressive policies" at home and abroad.