Boris Johnson has held talks with senior members of Donald Trump's team as the Government seeks to strengthen its links to the US president-elect before he takes office.
The Foreign Secretary met Mr Trump's son-in-law Jared Kushner and the president-elect's chief strategist Steve Bannon after flying to New York on Sunday on a hastily-arranged trip.
Mr Johnson will also meet key Republicans in Washington.
The meeting came after Theresa May condemned Mr Trump's comments about groping women as "unacceptable".
But she indicated the special relationship between the UK and US would flourish when he was in the White House.
Mrs May, who is expected to meet Mr Trump in the spring, said she has had two "very good, positive" conversations with Mr Trump.
Asked about a 2005 recording of Mr Trump bragging to TV host Billy Bush about women and how he could "grab them by the pussy" because of his celebrity status, Mrs May was blunt in her response.
Asked "as a woman" how she felt about the comments, Mrs May told Sky News: "I think that's unacceptable, but in fact Donald Trump himself has said that and has apologised for it.
"But the relationship that the UK has with the United States is about something much bigger than just the relationship between the two individuals as president and prime minister.
"That's important, but actually we have a long-standing special relationship with the United States.
"It's based on shared values and it is a relationship where, actually in the UK, we feel we can say to the US if we disagree with something that they are doing."
The status of the transatlantic relationship has been the subject of intense scrutiny since Mr Trump won the US presidential election in November.
That interest has been partly fuelled by the president-elect's apparent close relationship with the former Ukip leader Nigel Farage.
Meanwhile both Mrs May and Mr Johnson have been critical of the tycoon's comments in the past.
One controversy followed the president-elect's comments about parts of London being no-go areas for the police.
Mr Johnson said then: "The only reason I wouldn't go to some parts of New York is the real risk of meeting Donald Trump."
Mr Johnson's visit followed talks between the Trump camp and Mrs May's closest advisers Nick Timothy and Fiona Hill.
Mr Trump has tweeted that he was looking forward to meeting the Prime Minister in Washington in the spring, describing long-time US ally Britain as "very special".
A date for the meeting is yet to be revealed, but it is expected to come within weeks of Mr Trump's inauguration on January 20.
Mrs May said: "I have had two very good, positive conversations with Donald Trump already - I think we are going to look to build on that relationship for the benefit of both the US and the UK.
"I think that is something that is optimistic and positive for the UK for the future."
Mr Johnson's US visit will also see him meet key figures in Washington including House Speaker Paul Ryan and senators Bob Corker and Mitch McConnell.
A Foreign Office spokesman said the visit followed a successful meeting last month between the Prime Minister's chiefs of staff and Mr Trump's team.
"The discussions will be focused on UK-US relations and other foreign policy matters," the spokesman said.