LONDON (AFP)
King Charles III heads to the United States on Monday with transatlantic tensions over the Iran war threatening to intrude on the landmark visit.
Both Buckingham Palace and the British government have said the four-day trip will honour the historic relationship between the two countries as the US marks 250 years of independence.
Charles's first US state visit as monarch comes at the request of the UK government and President Donald Trump and will be made with Queen Camilla, according to the palace.
However, as the American leader's war with Iran drives a rare wedge between London and Washington, it has generated considerable controversy.
Trump has repeatedly lambasted British Prime Minister Keir Starmer over his war opposition, alongside his government's immigration and energy policies.
"This is not Winston Churchill that we're dealing with," Trump grumbled in March, adding the so-called special relationship was "not like it used to be".
In turn, Starmer has stepped up his public criticism of the war, while stressing the breadth and depth of UK-US ties in defending the state visit. An early April YouGov poll found 48 percent of Britons support cancelling it.
"Often what the monarchy is able to do, through the bonds that they build, is reach through the decades in a situation like this," Starmer told MPs when asked why the trip was going ahead.
Trump -- a vocal admirer of the royals whose mother was Scottish -- told the BBC on Thursday the visit could "absolutely" help repair relations, praising the king as "fantastic".
The UK's freshly-appointed ambassador to the US Christian Turner said the state visit was "important" for the countries' ties.
The king's relationship with the president "is a very personal one, the deep affection and respect they hold", Turner told NBC News.
'Politics'
Charles, 77, showcased his diplomatic skills during Trump's state visit to Britain last September, with Royal Holloway University of London monarchy expert Craig Prescott noting he is "generally very good" at navigating such occasions.
The first British monarch to address Congress since his mother, the late queen Elizabeth II, in 1991, he will mark the two countries' shared history and deep ties, the palace has said.
The visit, which will see the royals have tea with Trump and first lady Melania and attend a state dinner, appears meticulously planned to avoid unscripted moments.
Only photographers will capture Tuesday's Oval Office meeting between Trump and Charles, limiting chances for the king to be blindsided by the unpredictable US leader and reporters.
Charles and Camilla will visit New York on Wednesday, touring the 9/11 memorial, before departing Thursday for Bermuda for his first visit to a British overseas territory as monarch.