Liz Truss will have her first meeting as Prime Minister with Joe Biden this Sunday, it is understood.
The US President is one of a string of world leaders Ms Truss will meet as they fly to Britain for the Queen's state funeral on Monday.
She will meet President Biden - who she previously met as Foreign Secretary - at Downing Street, as well as the leaders of Ireland, Canada and Poland.
On Saturday she will also meet the Prime Ministers of Australia and New Zealand at Chevening, the Foreign Secretary’s grace-and-favour home in Kent, because the PM's country residence Chequers is undergoing renovation.
Her meeting with Ireland's Taoiseach could prove a crucial showdown as tensions mount over Brexit, with the UK refusing to allow certain checks on goods crossing the Irish Sea from Britain to Northern Ireland.
Yet the high-stakes meetings will not count as formal “bilaterals” because the government is still in national mourning for the Queen.
That means there will likely be no photos or video footage of the leaders meeting, and the UK government is unlikely to say what they have discussed.
Asked if the period of mourning was being used as an excuse to lack transparency, a No10 spokeswoman said: “I wouldn’t agree with that at all.”
Liz Truss has met Joe Biden before when she was Foreign Secretary but this will be their first meeting since she was made Prime Minister.
Ms Truss will meet Australian Prime Minister Anthony Albanese, New Zealand Prime Minister Jacinda Ardern, Irish Taoiseach Micheál Martin, Canadian PM Justin Trudeau, Poland's President Andrzej Duda, and US President Joe Biden.
Representatives from around 200 countries are set to be at the funeral with only a handful - including Russia, Belarus and Myanmar - not invited.
Last week the Foreign Office issued guidance to world leaders and royals visiting the capital for the state funeral, with 2,000 people expected to join the congregation on Monday.
Officials have urged them to travel to the ceremony on buses provided by the government from an undisclosed location and refrain from using private vehicles.
According to Politico, the Japanese Emperor Naruhito and Empress Masako are among those expected to board the bus along with royalty from Spain and Belgium while the US president will make his own arrangements.
Asked whether it was correct Emperor Narhuto would be using the shuttle service, a No 10 spokeswoman replied: "I wouldn't get into specific arrangements.
"Some arrangements will differ depending on the needs of the different leaders so I'm not going to speculate."
China will also still be allowed to send representatives to the Queen’s funeral across the street at Westminster Abbey - angering some MPs.
In a letter to the Commons and Lords Speakers, a group of MPs and peers said it was "extraordinary that the architects of genocide" against Uighur Muslims had been asked to attend.
But an official delegation from China has been banned from attending the Queen’s lying-in-state, it emerged today.
Commons Speaker Sir Lindsay Hoyle refused a request after Beijing sanctioned five MPs and two peers last year, Politico and then the BBC reported.
A spokeswoman for Sir Lindsay declined to comment.
