Donald Trump has insisted that the King shares his conviction that Iran must never be permitted to develop nuclear weapons, a claim likely to cause unease within royal circles given the monarch's constitutional neutrality.
The US President made the remarks during a White House state dinner held in honour of the visiting King and Queen Camilla, following bilateral discussions earlier in the day. As head of state, the King traditionally remains above party politics, making Mr Trump's public declaration of his views potentially embarrassing for royal aides.
Speaking at the white-tie event on Tuesday evening, Mr Trump stated: "We're doing a little Middle East work right now… and we're doing very well. We have militarily defeated that particular opponent, and we're never going to let that opponent ever, Charles agrees with me even more than I do, we're never going to let that opponent have a nuclear weapon. They know that, and they've known it right now, very powerfully."
The comments follow repeated calls from Liberal Democrat leader Sir Ed Davey for the trip to be cancelled before the King's four-day state visit commenced on Monday. Sir Ed had expressed concerns about the monarch meeting Trump, telling the Commons earlier this month: "President Trump is one of the most unpredictable people we have seen on the world stage and I hope he does not embarrass our monarch."
In response to Trump's remarks, a Buckingham Palace spokesperson said: "The King is naturally mindful of his Government's long-standing and well-known position on the prevention of nuclear proliferation."
Despite the potential diplomatic awkwardness, a certain rapport appears to have developed between Trump and the King, with Trump photographed touching the King's knee during their bilateral meeting. Following the discussions, Trump told reporters: "It was a really good meeting. He's a fantastic person. They're incredible people and it's a real honour."
During his state dinner speech, the King subtly suggested the purpose of his visit was to "put the 'special' back into our relationship", drawing a parallel with Queen Elizabeth II's efforts almost 70 years ago. He spoke of the enduring ties between Britain and America, implying his visit mirrored events in the aftermath of the 1956 Suez Crisis, when Elizabeth toured the US to help mend strained relations. Britain had been left humiliated after America refused to support its campaign with France to regain control of the Suez Canal from Egypt, a brief conflict that marked the end of the UK's role as a global military power.
Addressing dinner guests, who included Amazon founder Jeff Bezos and golfer Rory McIlroy, the King remarked: "And yes, we have had our moments of difficulty even in more recent history. When my mother visited in 1957, not the least of her tasks was to help put the 'special' back into our relationship after a crisis in the Middle East." Some guests laughed when the King added: "Nearly seventy years on, it is hard to imagine anything like that happening today…"
The King's most diplomatically sensitive state visit to date unfolds against a backdrop of criticism from Trump directed at Prime Minister Sir Keir Starmer over the war in Iran. Relations between the two men have been fractious, with Trump branding the UK's approach to the Iran war "terrible" and repeatedly criticising Sir Keir, at one point describing him as "not Winston Churchill."
A ceremonial welcome was staged for the King and Queen Camilla on the White House's south lawn on Tuesday, where Trump praised the "special relationship" between America and the UK, telling the King "we hope it will always remain that way" and declaring "Americans have had no closer friends than the British."
Later that day, the King delivered a historic address to Congress on Capitol Hill, becoming only the second British monarch to do so after his mother Queen Elizabeth II in 1991, and the first British king. He told the assembled politicians, who offered multiple standing ovations, that the partnership between the two nations is "more important today than it has ever been."
On Wednesday, the King and Queen Camilla are scheduled to commemorate the 25th anniversary of the September 11 terrorist attacks by laying flowers at one of the memorial pools in New York.
