The King and Queen have begun their four-day US tour that has taken on even greater prominence after the White House Correspondents’ dinner shooting and amid acrimony between the close allies.

The state visit is by ‌far the most high-profile and consequential of the King’s reign, marking the 250th anniversary of the US declaration of independence from British rule.

He is the first ‌British monarch in two decades to visit the US.

It also comes amid tense political relations after US President Donald Trump called British Prime Minister Sir Keir Starmer a “loser” and “no Winston Churchill” for refusing to get involved in the Iran war.

The King and Queen touched down at Joint Base Andrews, near Washington DC, about 2.30pm on Monday (local time) and headed to the White House for a private meeting with Trump.

The week’s schedule includes a speech to Congress, a lavish state dinner at the White House and a stop in New York City.

US Protocol Chief Monica Crowley greets the royals upon their arrival. Photo: AAP

On arriving in Washington, the King and Queen had a private tea with the President — an unabashed lover of the British royal family who ⁠regularly describes the monarch as a “great man” — and his wife, first lady Melania Trump.

The 77-year-old King, ‌who is still being treated for cancer, will address Congress on Tuesday (US time) — just the second time a British monarch has done so.

The royals will then head to New York where ​they will commemorate those ‌killed in the September 11, 2001, attacks before the 25th anniversary. The Queen will also mark the centenary of children’s stories featuring Winnie the ​Pooh.

The US trip concludes in Virginia with the King meeting people involved in conservation work, a nod to his half-century of environmental campaigning.

The Trumps warmly greeted the visiting royals at the White House. Photo: AAP

The long-planned visit has become enmeshed in a political spat between the two countries’ governments over the US-Israeli war on Iran, which led Trump to voice deep displeasure ‌with UK authorities for ‌failing to support the ⁠offensive.

Saturday’s shooting at the White House Correspondents’ Association dinner in Washington, ‌with Trump and officials ‌in his administration the ⁠likely targets, according to the US acting Attorney General, has cast a further pall over the visit.

Sharing a cup of tea on day one of the state visit. Photo: AAP

Buckingham Palace said the ​trip would still go ahead as planned following discussions between British and US authorities to determine if the incident would affect the royals’ plans.

“The King and Queen are most grateful to all those who have worked at pace to ensure this remains the case and are looking forward to the visit getting under way tomorrow,” a palace spokesperson said on Sunday.

Starmer’s government hopes the visit will shore up the future of the two allies’ “special relationship”, which is at its lowest point ​since ​the Suez Crisis in 1956.

While Trump has eased his criticism of Britain in recent days over its response to the Iran war, an internal Pentagon email has set out how the US could review its position on Britain’s claim to the Falkland Islands as punishment for its lack of support, once again straining ties.

One issue off the table during the visit is the Jeffrey Epstein scandal. Royal sources said it wouldn’t be possible for the King or queen to ​meet any victims of Epstein during their tour, as some have requested, because of potential effect on possible criminal cases.

The King’s brother, Andrew Mountbatten-Windsor, whose reputation and royal standing ​has been destroyed over his links to ⁠the late US sex offender, is faces police inquiries over his connections.

The former prince Andrew has denied any ​wrongdoing.

-with AAP