DIPLOMATS were yesterday scrambling to salvage the Iran nuclear deal after Donald Trump dramatically withdrew the US from the Joint Comprehensive Plan of Action (JCPOA).

The move was branded “deeply reckless and irresponsible” by a senior SNP MP .

Boris Johnson said Britain would not “walk away” from the agreement, despite fears that Trump would make good on his threat to impose the “highest level” of sanctions on Tehran, which could trigger a new confrontation in the region.

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Chancellor Angela Merkel said Germany remained committed to the deal while French foreign minister, Jean-Yves Le Drian, insisted it was not “dead”.

In Tehran, supreme leader Ayatollah Ali Khamenei voiced defiance, saying Trump “cannot do a damn thing”, while legislators in the Iranian parliament burned a paper US flag.

Stephen Gethins, the SNP’s spokesperson on international affairs and Europe, told the Commons: “The JCPOA has illustrated the importance of our relationship with our European partners, who are after all our closest allies. This work illustrates the painstaking effort that goes into seeking a diplomatic way forward.”

He said Johnson was right to mention the reduction in low-enriched uranium and other achievements of the deal after a long and painstaking process.

However, he added: “Does the Foreign Secretary agree that this move by President Trump is deeply reckless and irresponsible and has undermined the importance of the diplomatic process?

“Given what appears to be the UK’s lack of influence and the Foreign Secretary’s appeal on the president’s favourite TV show, does that not illustrate even more why we have such an important relationship with the EU in tackling the issue?”

Johnson sidestepped the question and said that as well as working with the US, the Government also worked with our European allies, adding: “As the Prime Minister has said many times, we may be leaving the EU, but we are not leaving Europe.”

He said that the Government continued to believe the agreement was “vital” to UK national security and had done its “utmost” to persuade Trump not to abandon it.

It was up to the US to spell out the way forward and Johnson urged the administration not to take any action which would hinder the efforts of the other parties to make it work.

“For as long as Iran abides by the agreement ... then Britain will remain a party to the JCPOA. Britain has no intention of walking away,” he said.

“Instead we will co-operate with the other parties to ensure that while Iran continues to restrict its nuclear programme, then its people will benefit from sanctions relief in accordance with the central bargain of the deal.”

The International Atomic Energy Authority – the global watchdog responsible for monitoring the agreement – said in a statement that “as of today” Tehran was continuing to honour its commitments.

Johnson’s comments came amid fears that re-imposing US sanctions could hit European firms – which have led the way investing in Iran under the JCPOA – particularly hard.

Speaking in the White House on Tuesday, Trump said the agreement – seen as the key diplomatic legacy of his predecessor Barack Obama – was “defective at its core”.

He said: “If we do nothing, we know exactly what will happen. In just a short period of time, the world’s leading state sponsor of terror will be on the cusp of acquiring the world’s most dangerous weapon.”

The JCPOA was signed by the US, China, Russia, Germany, France and Britain in 2015 after years of tortuous negotiations. Under its terms, Iran agreed to scale back key elements of its nuclear energy programme associated with the development of a nuclear weapon in return for the easing of economic sanctions.