Boris Johnson has called for a "Trump deal" on Iran.
The Prime Minister has said the US President is the "one guy" who can negotiate a new nuclear pact amid escalating tensions.
Mr Johnson said the existing deal was "bad" and had "many defects", in a break from previous UK policy, and called for a new agreement.
In an interview with a US broadcaster, he praised the confrontational business mogul-cum-president Donald Trump, who pulled out of the nuclear deal, as the leader to broker a new one.
Mr Johnson's calls for a replacement to the Joint Comprehensive Plan of Action (JCPoA) - also known as the Iran nuclear deal - quickly earned him praise from the president, who described him as "a winner".
However, the PM's comments came as he released a joint statement with German Chancellor Angela Merkel and French President Emmanuel Macron, expressing their "continued commitment" to the JCPoA.
The statement from the UK, Germany and France after the leaders met in New York said it is "clear to us that Iran bears responsibility for this attack" as they condemned it "in the strongest terms".
Mr Johnson's comments came after he formally blamed the Islamic republic for attacks on oil facilities in Saudi Arabia, and as he prepares to meet the nation's president Hassan Rouhani and Mr Trump in separate meetings on Tuesday.
"If it was a bad deal, and I'm willing to accept that it had many, many defects, then let's do a better deal," the PM said in an interview at the residence of the UK consulate general in New York.
"And I think there's one guy who can do a better deal and one guy who understands how to get a difficult partner like Iran over the line and that is the president of the United States.
"So I hope that there will be a Trump deal, to be totally honest with you."
But Downing Street moved to stress that Mr Johnson supports the nuclear deal.
Also in the interview, Mr Johnson said military force over Iran is "not something that I think will necessarily help the situation".