Britain must accept the Iran nuclear deal is “dead” and join America in trying to force Tehran back to the negotiating table, former defence secretary Liam Fox said tonight.
Mr Fox, who was in the cabinet until July, will use a speech in Washington to warn that the 2015 agreement was "flawed" from the start and that attempts to keep it alive are "futile".
The intervention is effectively a call for Boris Johnson to join Donald Trump in withdrawing from the deal and comes amid escalating tensions in the wake of the attack on two Saudi oil facilities.
Iran’s supreme leader on Tuesday ruled out talks with US officials “at any level”, appearing to end hopes of a meeting between Mr Trump and Hassan Rouhani, Iran’s president, at the United Nations in New York next week.
Meanwhile King Salman of Saudi Arabia spoke for the first time since the drone attack over the weekend, calling on fellow world leaders to deliver a united message of condemnation.
He called on the international community "to shoulder its responsibility in condemning the perpetrators" and "clearly confronting" those behind it.
The threat of imminent military action appeared to have faded, for now at least, as the Trump administration sought proof to back up its suspicion that Iran was behind the attacks.
Since pulling the US out of the Iran nuclear deal, which was struck by his predecessor Barack Obama, Mr Trump and his officials have attempted to lobby other signatories to do likewise.
Britain has remained in the pact, which swapped the cessation of Iran’s nuclear programme for sanctions relief, along with France, Germany, Russia, China and the European Union, as well as Iran itself.
But since Mr Johnson became prime minister there has been renewed lobbying from the US administration to move Britain closer to the its position and perhaps even leave the deal entirely.
Mr Fox, who was international trade secretary until the summer and remains well-connected in Republican circles, will reveal his opposition to the deal today in a speech to the Heritage Foundation, a right-leaning think tank.
“Following the decision of President Trump to withdraw, the Joint Comprehensive Plan of Action is dead and European attempts to salvage it are futile," Mr Fox writes in a piece for The Telegraph’s website previewing the speech.
"Britain should follow the US lead and operate a policy that would reduce Iranian oil exports to zero in an attempt to force a change of behaviour from the Khamenei regime.
"The agreement has been shown to give scant, and only short term, reduction in Iran’s ability to develop nuclear weapons. The original aim of halting Iran’s nuclear weapon programme now offers merely a delay with the problem left as a toxic legacy to future governments."
Saturday's drone attack on Abqaiq - the world's largest processing plant - and the Khurais oilfield have knocked out 5.7 million barrels per day (bpd), or six percent of global total, making it the biggest disruption to oil production in modern history.
Iran has denied it launched the attacks, with the Houthi rebels in Yemen - who Tehran backs - claiming responsibility.
But the Saudi defences failed to stop the missiles because they were pointing South to prevent an attack from Yemen, according to a senior US official talking to CBS News - raising suspicions the attack came from elsewhere.
The strike has intensified tensions between Iran and the Saudis. It has also decreased the chance of Mr Trump pivoting and seeking a new nuclear deal with Iran after years of its “maximum pressure” campaign.
Ayatollah Ali Khamenei, Iran’s highest authority, said: "Iranian officials, at any level, will never talk to American officials.”
He added: "If America changes its behaviour and returns to the nuclear deal, then it can join multilateral talks between Iran and other parties to the deal.”
Mike Pence, the US vice president, tweeted:
America’s maximum pressure campaign against the Iranian regime is working. And if Iran conducted this attack to pressure the President to back off, they will fail.
— Vice President Mike Pence (@VP) September 17, 2019
Mr Johnson talked to Angela Merkel, the German Chancellor, on Tuesday and agreed a “collective response” was needed over the attack, according to a read-out from Downing Street.
Meanwhile Germany is set to extend its embargo on weapons sales to Saudi Arabia for a further six months, despite calls in Berlin to ease the ban over growing tensions in the Gulf.
“I see no reason to change the government’s position on this matter,” Ms Merkel said on Tuesday, effectively shutting down calls from her own MPs to lift the ban.