US President Joe Biden and First Lady Jill Biden will meet the Queen at Windsor Castle later.
The couple will receive a guard of honour and tea during the visit, which comes after they last met during the G7 summit in Cornwall.
The Queen will greet the Bidens inside the castle grounds, where a guard of honour formed of The Queen’s Company First Battalion Grenadier Guards will give a royal salute, and the US national anthem will be played.
Mr Biden will accompany the officer commanding the guard of honour, Major James Taylor, and Major General Christopher Ghika, to inspect the honour guard.
After the formal ceremonial arrival, the Bidens will join the monarch inside the castle for tea.
In 2018, the Queen accompanied then-president Donald Trump to inspect the guard of honour at Windsor.
Pictures appeared to show Mr Trump walking in front of the Queen, seen by some as a diplomatic faux pas.
Democratic strategist Laura Fink told Sky News that Mr Biden will see the visit as huge honour, and she wouldn’t be surprised if they had a lot in common.
She said: “It’s funny because with Donald Trump, he said it’s the best time she’s had in 25 years following the event and I thought that was characteristic of his bombast.
“I think it’s going to be 180-degree shift with Joe Biden.
“He is understated, he’s someone who connects with people on a deeply personal level.
“I think right now with the recent passing of Prince Philip and the experiences that President Biden has had with loss in his own life, he tends to lead with empathy and connection and of course good humour.
“So I think it’ll be a much more understated event with fewer stories of the presidential eclipse with President Trump walking ahead of the Queen, and more about the connection between two individuals that have led their countries for quite some time.”
There have been 14 US presidents during the Queen’s 69-year reign – from Harry S Truman to Mr Biden.
Mr Biden will be the 13th American leader to meet the monarch, with Lyndon B Johnson the only one the Queen did not meet.
The Royal Family is seen as a hugely important diplomatic asset for the UK.
The emphasis on shared interests started on Friday with the Duchess of Cambridge hosting First Lady Jill Biden during a visit to a school in Cornwall, before joining the Queen and other members of the family at a reception for the G7 leaders.
Lord Darroch, who was the UK’s ambassador in Washington during the Trump administration, said nothing compares to the Queen’s subtle influence.
He said: “There is just an extraordinary fascination which is very lucky for us, they (the Royal Family) are a huge national asset, and that helps greatly, I think.
“It’s part of soft power diplomacy. A big part.”
Speaking about how the Queen will prepare for the meeting he said: “Yes, there will be a Foreign Office briefing provided for her and, yes, she will read it and she will get it all, she will pack it away and that will be part of the material for her conversation with him.
“But she’s just so experienced at doing this, I’m sure she can manage without the briefing, but she will take the briefing and she will absorb it.”
The visit from the president concludes a very busy weekend for the 95-year-old monarch.
On Friday, she travelled to Cornwall for the G7 leaders’ reception, before heading back to Windsor for her official birthday parade on Saturday.