- "Let's dial this down," the UK prime minister said, adding that 'I don't want a military conflict between us, the United States and Iran,' in an interview with the BBC.
- Johnson also appeared to mock Trump's boastfulness, calling him 'a great deal maker, by his own account.'
- The comments came as the UK defence secretary said the country would need to forge new defence alliances with other countries as the US risks '[withdrawing] from its leadership around the world.'
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Boris Johnson has told Trump to "dial down" his conflict with Iran and step back from outright war.
The UK Prime Minister said on Tuesday that war in the region would not be in the UK's interests.
"Let me be very clear. I don't want a military conflict between us, the United States and Iran," he told the BBC in a live interview inside his Downing Street residence.
"Let's dial this down."
In comments which appeared to mock the president's boastfulness, Johnson also insisted that the Iranian nuclear deal should be replaced with a new deal negotiated by the president.
"President Trump is a great deal maker," Johnson said, before cheekily adding "by his own account, and many others."
"Let's work together to replace the JCPOA and get the Trump deal instead."
Johnson's comments came after the UK defence secretary said the country would not automatically back the US in future wars.
"The assumptions of 2010 that we were always going to be part of a US coalition is really just not where we are going to be," Ben Wallace told the Sunday Times.
Wallace said that Trump's isolationist policy, in which it risks "[withdrawing] from its leadership around the world" meant the UK would need to look to other international defence allies in future.
"We are very dependent on American air cover and American intelligence, surveillance, and reconnaissance assets," he said.
"We need to diversify our assets."
Wallace's comments were described by the former Conservative foreign secretary Jeremy Hunt on Monday as "courageous and right."
"American commitment to leadership of the alliance of democracies is weaker than it's been in some time," Hunt told BBC Newsnight.
"Ben Wallace pointing out that we can't take American leadership for granted is courageous and right."
Trump threatens to cut off intelligence ties with the UK
"Congress has made it clear they will want an evaluation of our intelligence sharing," one senior US official told the Guardian , with another official adding that "Donald Trump is watching closely."
However, Johnson refused to rule out going ahead with the Huawei deal, telling the BBC that "The British public deserves access to the best possible technology."
He added: "If people oppose one brand or another they have to tell us what's the alternative?"
- Britain condemns Iran's 'reckless and dangerous' attacks after US bases are struck by Iranian missiles
- Boris Johnson accused by the UK's former national security chief of being 'caught short' by the Iran crisis
- The United States' allies warn Trump that terrorists 'would be the only winners' of war with Iran