The Queen will hold her first face-to-face meeting with a world leader in more than a year when she hosts President Joe Biden at Windsor Castle later this month.
Biden and First Lady Jill Biden will visit Windsor on June 13, after the G7 summit in Cornwall, when they are expected to take tea with Her Majesty.
Britain will be the first foreign country the President has visited since his inauguration in January, and on June 10, before the summit starts, Biden will meet Boris Johnson to "affirm the enduring strength of the special relationship", the White House said.
Johnson was the first European leader to receive a call from Biden after he took the oath of office in January, when the President said he wanted to "strengthen" the special relationship. His meeting with the Queen will be regarded as a key part of that process and is likely to be followed by a full State visit at a later date.
Buckingham Palace said the meeting would abide by Covid restrictions, meaning the Queen and the President will wear masks during indoor parts of their meeting, though they are likely to discard them and socially distance when outside.
Buckingham Palace said the details of the meeting are still being worked out, but it is understood that it will be broadly similar to President Donald Trump's visit to Windsor in 2019.
On that occasion the President inspected an honour guard of soldiers, took tea and posed for a photograph with the Queen and Melania Trump. The Prince of Wales was also present for the visit, and is expected to meet the Bidens.
The Queen, who has received two doses of Covid-19 vaccine, has been holding the vast majority of her meetings virtually, including audiences with foreign ambassadors.
It will be her first meeting in person with a foreign head of state since the pandemic hit, and the first since the death of the Duke of Edinburgh in April.
With the exception of Lyndon B. Johnson, the Queen has met every US president during her 69-year reign, starting with Harry S. Truman. Biden will be the 13th president she has met.
Jen Psaki, the White House press secretary, said: "This trip will highlight America's commitment to restoring our alliances, revitalising the Transatlantic relationship, and working in close cooperation with our allies and multilateral partners to address global challenges."
Biden's visit to Windsor will come the day after Trooping the Colour, the Queen's official birthday celebration. For the second year running, the traditional ceremony in London has been cancelled because of Covid, but a smaller event is being considered within the grounds of Windsor Castle.
After he leaves the UK, the President will travel to Brussels for a Nato summit on June 14, followed by a US-EU summit the following day.
He will also meet Turkish President Recep Tayyip Erdogan to discuss "bilateral and regional issues", before flying to Geneva where he will hold a summit with Russian President Vladimir Putin.
Biden said he was considering retaliation after the White House linked Russia to a recent cyberattack against meat processing giant JBS.
He said: "We're looking closely at that issue."
Asked if he thought Putin was testing him ahead of their summit, Biden said "No."
But the US President said he would discuss hacking during the G7 summit, and with Putin.
Psaki said: "We expect this to be an issue of discussion throughout the President's trip.
"We're in direct touch with the Russians. President Biden certainly thinks that President Putin and the Russian government has a role to play in stopping and preventing these attacks."