The King is still set to visit the US next month despite growing tensions between Sir Keir Starmer and Donald Trump over Iran, according to reports.
Charles is reportedly expected to be met with a display of American military strength when he undertakes the three-day trip amid a strained time for the special relationship.
The overseas tour has yet to be officially announced, but the King and Queen are expected to visit Washington and New York to mark the 250th anniversary of American independence.
Foreign secretary Yvette Cooper is believed to be accompanying the royals, following an escalating war of words between the prime minister and the president over the Middle East crisis.
Mr Trump said on Tuesday that he was “looking forward” to meeting Charles “very shortly”, despite calls for the historic royal trip to be postponed.
Asking whether his relationship with Sir Keir was damaged by the UK’s stance over the war, Mr Trump said the prime minister made a “big mistake” in his response to US calls for support and suggested his effort to strike a “good deal” on trade with Britain “probably wasn’t appreciated”.
The US president has previously branded the UK’s approach to the conflict “terrible” and repeatedly lashed out at Sir Keir, including describing him as “not Winston Churchill”, with the special relationship between the two allied nations appearing increasingly strained.
But The Times reports Charles’ trip, from 27 to 29 April, will be apolitical, with no big policy announcements expected.
The White House, Buckingham Palace and the British government are all determined the visit should go ahead, according to the newspaper, so that the King can pay tribute to Americans for their independence anniversary and following six months of planning that has involved royal aides doing a “recce” in the US.
“This will be a substantive visit from the King for the American people,” a source with knowledge of the plans told The Times.
The monarch is reportedly set to give a speech to Congress, highlighting the close ties between the UK and the US.
Mr Trump was feted with a second state visit to the UK, unprecedented for an American leader, last year.
The royal family’s soft power diplomacy is viewed as an important and unique way of engaging with the billionaire-turned-politician, who is well known for his love of the monarchy.
Senior Labour MP Dame Emily Thornberry is among those who have suggested it would be “safer to delay” Charles and Camilla’s state visit because of the Iran war, warning they could be left feeling “embarrassed” because of the current crisis.
A recent YouGov poll found 46 per cent of Britons believe the King should cancel the official visit and not travel to the US this year, while 36 per cent said it should go ahead and 18 per cent did not know.
