Donald Trump has called on the UK, its European allies and others to abandon the “defective” Iran nuclear deal.
The US president said the “time has come” for Britain, Germany, France, Russia and China to “break away” from the Joint Comprehensive Plan of Action (JCPOA).
Under the deal, Iran agreed to limit its nuclear programme and allow in international inspectors in return for the easing of economic sanctions.
Hours before Mr Trump’s remarks, Boris Johnson said the deal remains the “best way of preventing nuclear proliferation in Iran”.
He told MPs during Prime Minister’s Questions: “It is the best way of encouraging the Iranians not to develop a nuclear weapon — and we think that after this crisis has abated, which of course we sincerely hope it will, that way forward will remain.
“It is a shell that has currently been voided, but it remains a shell into which we can put substance again.”
At a White House press conference on Wednesday afternoon Mr Trump said the “very defective JCPOA expires shortly anyway and gives Iran a clear and quick path to nuclear breakout”.
“Iran must abandon its nuclear ambitions and end its support for terrorism.
“The time has come for the United Kingdom, Germany, France, Russia and China to recognise this reality.
“They must now break away from the remnants of the Iran deal – or JCPOA – and we must all work together towards making a deal with Iran that makes the world a safer and more peaceful place.”
However, on a visit to New York in September, Mr Johnson called for a “Trump deal” on Iran, describing the existing JCPOA deal as “bad” with “many defects”.
The president claimed Iran appeared to be “standing down” following the missile attack, which he said was a “very good thing for the world”.
And he also announced that the US would be imposing additional “punishing” economic sanctions on the Iranian regime until the country “changes its behaviour”.