"He has to see the British head of state", adding that other details of the trip had not been finalised.
But the PM stressed that the UK-US special relationship meant that she could fully air disagreements, which Britain had with American policy, with the President.
President Trump will meet Queen Elizabeth II during his visit to Britain next month, and many Brits are not amused. "This is not something that we agree with", May said.
The President's advance teams will be in the United Kingdom next week to sort out more details of the visit, st to be scheduled on Friday, July 13.
"Putting his foot on the ground of British soil, it's job one - very, very important, very symbolic", Robert Wood Johnson said when asked whether Trump's visit would involve seeing the queen.
Neymar picks up injury during Brazil's training ahead of Costa Rica match
Costa Rica performed well but fell agonisingly short against one of the tournament favourites. Brazil has just one point after their first game draw against Switzerland.
Paul McCartney brings James Corden to tears on "Carpool Karaoke"
They then leave the auto to visit the barber's shop mentioned in the song - leaving the owner in sheer disbelief. The TV personality gushed, "I think this is an afternoon none of us will forget".
All the times Priyanka Chopra and Nick Jonas were spotted together
Priyanka recently accompanied the American singer to his cousin's wedding in New Jeresy and was seen having a great time there. He shared the story with, "Her (heart-eyes emoji)".
A spokeswoman for Buckingham Palace declined to comment.
London Mayor Sadiq Khan this week defended the right of residents to protest about the President's visit while speaking to singer Jessie Ware on a podcast.
"The US is one of the great champions of liberty in the world", he said.
Sam Gyimah, universities minister, took to Twitter to express his dismay with the policy.
The Trump administration's "zero tolerance" policy refers all undocumented adults for criminal prosecution, a break with past administrations who limited criminal referral for most adults who illegally cross into the USA with their juvenile family members.
The commander-in-chief has previously been promised a full state visit when Theresa May visited Washington previous year, but officials have previously confirmed Mr Trump would not be taking up the offer this time around.
Pictures and video of youngsters in cages and audio of confused children crying for their parents has been condemned by Republican lawmakers, church groups and influential business leaders - as well as Theresa May.