Mrs. May is hoping to lay a groundwork for a trade deal with the United States, as she tries to negotiate Britain’s departure from the European Union.
But in his interview with The Sun, published Thursday night, Mr. Trump said that if the prime minister persisted in seeking a so-called soft exit from the European Union, sticking close to its rules on goods, she could forget about a separate pact with the United States.
“If they do that,” the paper quoted him as saying, “then their trade deal with the U.S. will probably not be made.”
Hours before the interview was published, Mr. Trump was asked about Brexit at a news conference and said, “It’s not for me to say about the U.K.”
But speaking to The Sun, he described the prime minister’s approach to Brexit as “very unfortunate,” and said, “I actually told Theresa May how to do it, but she didn’t listen to me.”
He had much warmer words for Boris Johnson, the ambitious British politician who just quit as foreign minister in an open break with Mrs. May, and is seen as one of her primary rivals within the Conservative Party. Mr. Johnson, he said, would “make a great prime minister.”
For the president to criticize and politically undercut one of his closest international allies, on her home turf, is an extraordinary breach of protocol, but if anything seems clear at this point, it is that there is no reason to expect the expected.
The two leaders posed for photographs after Mr. Trump arrived at Chequers on Friday morning — he in a blue suit, Mrs. May in a red jacket and dark trousers — and answered a few questions before going behind closed doors. But he didn’t answer one question: Asked whether he regretted his comments, Mr. Trump rolled his eyes and shook his head.
“We had a dinner where I think we’ve never had a better relationship,” Mr. Trump said, adding that he and Mrs. May had spoken for an hour and a half on Thursday, discussing trade, defense and counterterrorism.
Perfectly reasonable, or ‘wholly outrageous’? The response in Britain
On Friday, Mrs. May’s hard-line opponents used Mr. Trump’s comments to bolster their argument that the government’s plans for Britain’s withdrawal from the European Union, or Brexit, should be torn up in favor of a cleaner break with the bloc.
Speaking to the BBC, Jacob Rees-Mogg, a Conservative lawmaker and one of Mrs. May’s pro-Brexit critics, argued that Mr. Trump had been “perfectly reasonable,” simply reflecting the reality of the government’s proposals.
Alan Duncan, a minister of state at the Foreign Office, suggested that Mr. Trump had spoken to The Sun before reading the details of Mrs. May’s latest Brexit plan, which aims to keep some close economic ties to the European Union.
But Simon Fraser, formerly one of Britain’s most senior diplomats, described the president’s “patronizing put-down” of Mrs. May as “wholly outrageous.”
“Normally I don’t feel sorry for Theresa May,” Emily Thornberry, a foreign affairs spokeswoman for the opposition Labour Party, told Sky News. “I don’t think that feeling sorry for a prime minister is a very good look, but this morning I feel sorry for her.”