King Charles III and Queen Camilla meet Donald Trump and the First Lady Melania Trump at the White House - watch live
The royals have officially started their four-day state visit - here's a look at their warm welcome in pictures
This is the biggest diplomatic challenge of King Charles's reign, writes our royal correspondent, and there are high stakes
The Palace says the programme will go ahead largely as planned and further security talks have taken place after a gunman gained access to an event attended by Trump on Saturday
We're now seeing images of the King and Queen sitting down for tea with the president and first lady at the White House.
The spread appears to feature finger sandwiches, cakes, honey, with a pot of tea being poured by a staff member.
Image source, Pool
Image source, Pool
Image source, Getty Images
Image source, Getty Images
Image source, Reuters
Image source, Getty Images
Image source, ReutKing Charles and Queen Camilla have been invited into the White House with US President Donald Trump and First Lady Melania Trump.
Before entering the building, the four stood in a line posing for the waiting media, with the King and Trump appearing to exchange friendly remarks.
The president and first lady will now host a private tea, with a garden party to be held later.
King Charles and Queen Camilla have just arrived at the White House.
They're being greeted by President Donald Trump and First Lady Melania Trump.
You can watch live at the top of this page.
Image source, Reuters
Image source, POOL
Image source, POOL
Image source, Getty ImagesToday's visit marks the first British state visit to the US since Queen Elizabeth II's trip in 2007.
The six-day visit saw the late Queen, accompanied by Prince Philip, meeting the then-US President George W Bush.
The Queen was honoured with a 21-gun salute ahead of a state banquet and visited a replica of the largest ship to carry English settlers across the Atlantic in 1606.
In a speech delivered at the banquet, the Queen toasted the UK-US relationship.
Her visit marked the 400th anniversary of the country's first permanent English settlement.
Sean Coughlan
Royal correspondent in Washington DC
Image source, Yui Mok - WPA Pool/Getty ImagesTrump and King Charles enjoy a lighter moment during the state banquet at Windsor Castle for last year's state visit
Thorny political relations
While the US president is a self-avowed fan of the royals, he regularly criticises the UK Prime Minister, Sir Keir Starmer, and dismissed UK aircraft carriers as "toys" compared with US equivalents. The King is, of course, the head of the British Armed Forces.
'Delicate balancing act'
State visits are carried out on behalf of the government, and royal sources recognise this trip is going to be a "delicate balancing act", but say there's a bigger picture of long-term US and UK friendship.
"Yes, we face current challenges, but the visit will also seek to celebrate our nations' historic ties and create the conditions for that partnership to continue long into the future," says a royal source.
The King's brother Andrew
There's personal pressure on the King too. After the scandal involving his brother Andrew Mountbatten-Windsor, it's highly likely that survivors of the late sex offender Jeffrey Epstein will be giving interviews complaining that the royal visitors are not meeting them during the visit.
Queen Camilla will be meeting campaigners against domestic abuse during her engagements.
Trump's admiration for the King:
Trump has been steadfast in his admiration for the monarchy and King Charles.
"I know him well, I've known him for years," the president told the BBC last week about the King. "He's a brave man, and he's a great man."
Whether or not that admiration is reciprocated is hard to say. Because when you ask insiders about how the King sees Trump, they tend to repeat how much Trump admires the King.
Daniela Relph
Reporting from Joint Base Andrews
At this moment in time, when you look at the two personalities of the men involved, it's hard to find a time when on paper they have felt further apart.
In the King you have a quiet, cautious, restrained kind of character who largely plays by the rules.
In President Trump you have someone who is much looser, who shoots from the hip, someone who is a little less predictable.
Both Buckingham Palace and the UK government are very aware of the jeopardy of this trip.
That is why, when you look at the detail of the programme, some of that jeopardy has really been squeezed out.
There aren't many moments - I counted just five - when we will see the president and the King together.
So there is an element of management.
The four day itinerary will see the royal couple welcomed at a formal ceremony at the White House and conduct a ceremonial military review.
First on the agenda, however, is an informal welcome by President Trump and the first lady.
They will host a private tea before the four attend a garden party with a wider array of guests.
Image source, Getty ImagesRoyal commentator Caroline Aston has just been speaking to BBC News.
She says, for someone still living with cancer, the state visit's "cost in physical and mental terms will be high" for King Charles.
"It just shows what a trooper he is and how he's very much inherited his late mother's spirit of service and duty," Aston says.
It's worth remembering that the King is 77 years old and is the oldest person to ascend to the British throne, she adds.
The King and Queen have now departed Joint Base Andrews, and will soon be arriving at the White House to meet US President Trump and First Lady Melania Trump.
There, they will be greeted for a private tea, before attending a garden party.
Image source, Getty Images
Image source, Getty Images
Image source, Reuters
Image source, ReutersAfter walking through a military guard of honour, a military band plays both the US and UK national anthems to the King and Queen.
The pair now enter a black car parked on the runway of the air base, before departing.
Image source, Getty Images
Image source, Reuters
Image source, Getty ImagesThe King and Queen are now being greeted by the welcoming party on the red carpet as they disembark the plane.
The pair were gifted flowers by two young children before being greeted by UK ambassador to the US Sir Christian Turner and the White House's head of protocol, Monica Crowley.
Image source, ReutersKing Charles and Queen Camilla can now be seen descending the stairs of the aircraft for their US visit, the first undertaken by a British monarch since 2007.
Several dignitaries, a guard of honour and a military band are there to meet them.
US President Donald Trump and First Lady Melania Trump will greet them at the White House later.
Image source, AFP via Getty Images
Image source, ReutersThe King and Queen are shortly due to depart the plane, marking the start of their four-day US state visit.
You can watch live above.
Image source, POOL
Image source, POOL
Image source, POOL
Image source, ReutersKing Charles III and Queen Camilla have just landed in the US.
They will soon be disembarking their plane and beginning their four-day state visit.
You can watch live at the top of this page.
We're seeing the first images now of a red carpet that is being rolled out at Joint Base Andrews, Maryland, ahead of the King and Queen's arrival.
A military band and honour guard are also pictured.
Image source, Getty Images
Image source, Getty Images