Trump has begun a trade war already with the EU, China and others. The interview overshadowed much of his first official trip to Britain in capitalized headlines and a torrent of TV coverage.
Mr Trump described Brexit as a "very tough situation. between the borders and the entries into the countries and all of the things", saying: "The only thing I ask is that she work it out so that we can have very even trade".
"Because we have enough difficulty with the European Union. He links immigrants to terrorism, specifically, rather than employment, which is actually part of what pushed up some of the Brexit negotiations". "We're not going to have this any longer", he stressed.
But even if Britain can extricate itself from the dense web of regulations and tariffs resulting from its decades of European Union membership, a US-UK trade deal would be easier said than done.
Trump declared as "fake news" his criticism of May in an early Friday interview in The Sun, eventhough the tabloid released a recording of the session.
"I only gave her a suggestion, not advice", Trump said.
However, he later said Ms May was doing a "fantastic job".
Protests are also planned at locations including Windsor, where Trump will meet with Queen Elizabeth II.
The body language of that highly symbolic meeting was always going to be closely scrutinized.
The Queen, the President and first lady Melania Trump all shook hands. Trump said the discussion "was really something".
"(Queen Elizabeth has) a great and lovely grace about her. The British press was divided over whether Trump simply stumbled over a bit of royal stagecraft or breached protocol.
The two leaders said they'd complete a trade deal between their countries as soon as the United Kingdom leaves the European Union, after Trump told the Sun newspaper in an interview published Thursday that an accord might not be possible because of her decision to maintain ties with the EU.
The Sun interview seemed to dash those hopes.
Trump said her plan would likely "kill" any UK-US trade deal.
During his news conference, Trump addressed a range of topics including his hope to address nuclear disarmament with Russian President Vladimir Putin during their upcoming Helsinki summit; defending his behavior at the recent North Atlantic Treaty Organisation summit; and proclaiming that immigration has been "bad for Europe".
In the court of Emperor Trump - as the Sun's political editor Tom Newton Dunn dubbed the White House on Thursday - nothing is certain. But at the Chequers news conference, Trump said he had been responding to the Sun's question about Johnson as a possible prime minister, adding: "He has been very nice to me".
Mr Duncan suggested the President had not seen the details of the plan when he gave the interview on Wednesday, while also stressing that the much-vaunted special relationship was about much more than Brexit. Mr. Trump's intervention was "very important, because if you can't do a trade deal with your closest ally, then who can you do a trade deal with?" said Jacob Rees-Mogg, a Tory MP who has been among the sharpest critics of Ms.
The FT also plays up the president's change of course, though with Brexit on its mind, saying "Trump switches tack on Brexit in bid to mend bridges with May".
In the interview, which took place at the U.S. Embassy in Brussels, the president also lashed out at the Muslim mayor of London, saying he had done "a bad job". As for Johnson, who was recently deposed, Trump said: "I think he would be a great prime minister".
May, standing at a lectern beside Trump, disagreed.
Trump is now involved in serious discussions about redesigning the presidential aircraft, which would include a new red, white and blue design, according to multiple reports. "Immigration is not a crime", said another.
Augustine Chukwuma Obodo, who wore a "Make America Great Again!" hat and a "Trump for President in 2020" shirt, said he wanted to make clear that not everyone found the protests amusing.
"It's called fake news", Mr Trump declared. So a lot of people don't like it. "I would have done it much differently", he added.
"Given Trump's appalling actions and rhetoric, he doesn't even deserve to look at a statue of Churchill let alone sit in his seat". Some are fearful that Trump will pull troops out of the region. He also said he will bring up the issue of Russian Federation meddling in the 2016 USA election. "I don't take questions from CNN". "I have a lot of respect for the prime minister", Trump said. "I think he has done a bad job on crime, if you look, all of the frightful things going on there, with all of the crime that is being brought in". We have seen it before.
Trump conceded that the North Atlantic Treaty Organisation meeting in Brussels earlier this week at times got "testy" over his demands that European nations increase their spending on defense, but he said it ended with "more unity" and "more spirit" and that Putin would see those headlines, not ones that talked about the alliance's divisions.
"This was an Obama disaster".
He added: "I didn't think they put it in, but that's all right".