Donald Trump has said the UK will “probably not” get a trade deal with the US, if the prime minister’s Brexit plan goes ahead.
He told The Sun the PM’s plan would “probably kill the deal” as it would mean the US “would be dealing with the European Union” instead of with the UK.
Downing Street has not yet reacted to Mr Trump’s remarks.
Theresa May has been making the case for a US free trade deal with Mr Trump, on his first UK visit as president.
She said Brexit was an “opportunity” to create growth in the UK and US.
Mr Trump also said that former Foreign Secretary Boris Johnson would make a “great prime minister”, adding “I think he’s got what it takes”.
In his interview, he renewed his criticism of London Mayor Sadiq Khan over last year’s terror attacks in the capital, saying he had done “a terrible job”.
The president and his wife were given a red carpet reception at Blenheim Palace, Oxfordshire on Thursday evening.
They were at a black-tie dinner with Mrs May as news broke of his interview with the newspaper, which said it was conducted while he was in Brussels.
After it was published, White House spokeswoman Sarah Sanders said the president “likes and respects Prime Minister May very much”, adding that he had “never said anything bad about her”.