Donald Trump is likely to meet the Queen when he visits the UK this July, the BBC understands.
They will either meet at Buckingham Palace or Windsor Castle, BBC North America editor Jon Sopel said.
The US president is to visit the UK on Friday, 13 July, after previously cancelling a trip amid claims he would face mass protests.
Downing Street called it a “working visit” – not the full-blown state visit Mr Trump was promised last year.
Mr Trump will hold talks with Mrs May, Downing Street said, with further details to be “set out in due course”.
The prime minister said she was “looking forward to welcoming President Trump to the United Kingdom for a working visit on July 13”.
The July date follows the Nato summit in Brussels which the president is expected to attend.
Downing Street and the White House hoped to co-ordinate releasing details of the trip, but Mr Trump’s spokeswoman Sarah Sanders apparently let slip the information first.
UK ambassador Sir Kim Darroch said he was “delighted” that Mr Trump would visit the UK.
Mr Trump cancelled a planned trip to London to open the new US embassy in Vauxhall earlier this year, complaining the move to an “off location” south of the Thames had been a “bad deal”.
But critics said his decision may have been driven by a fear of protests.
Foreign Secretary Boris Johnson tweeted that it was “fantastic” news Mr Trump was visiting.
Meanwhile his successor as mayor of London, Labour’s Sadiq Khan – who clashed with the US president over London terror attacks and Mr Trump’s proposed ban on Muslims entering the US – said the president would experience a city that chose “unity over division”.
Some have been suggesting that Mr Trump should avoid London, where protests are expected.
More than 33,000 people on Facebook have already said they will attend a protest organised by left-wing journalist Owen Jones.
Sir Christopher Meyer, a former British ambassador to the US, told the BBC’s Today programme: “Things can be organised in a way where he does not have to come into confrontation with or even hear demonstrators.”
Six Conservative groups – including the think tanks the Bow Group and the Bruges Group – have written to Mr Trump urging him to focus his visit on his “ancestral home” of Scotland, where his mother was born.
“A visit to London by the president is likely to draw major protests, crime and disorder, and we do not wish to see Britain or President Trump embarrassed by this,” Ben Harris-Quinney, chairman of the Bow Group, said.
“Many in Britain… wish for President Trump to be afforded the warmest of welcomes,” he added.
“Sadly that will not be the case in London.”
Lib Dem deputy leader Jo Swinson said the “scaled-down trip must not be met by scaled-down protests”.
Kate Allen, Amnesty International UK’s director, said: “When Donald Trump arrives on these shores, we and thousands of our supporters will very definitely be making our voices heard.”
Shadow home secretary Diane Abbott said on BBC One’s Question Time that she would not join protests, but defended the rights of others to do so – saying Mr Trump’s “actions and his attitudes have made him so frightening to so many people in this country”.
Culture Secretary Matt Hancock told the same programme that the US-UK relationship was “much deeper than any one person” and “we have to make sure that we influence the strongest economy on earth”.
“The United States kicked out more Russian diplomats than any other country in response to the Salisbury attack,” he said.
“They have been strong supporters when we have needed them recently in the face of Russian aggression.”
Theresa May was the first foreign leader to visit Mr Trump in the White House following his inauguration in January 2017.
She conveyed an invitation from the Queen for Mr Trump to come for a state visit – a formal occasion with much pomp and ceremony.
Mr Trump accepted the invitation but a date has yet to be set, amid speculation it has been postponed indefinitely.
Plans for a working visit to the UK in 2018 were announced when Mr Trump met Mrs May at the World Economic Forum in Davos in January.