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.
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.
Mr Trump told The Sun newspaper that the UK’s blueprint for its post-Brexit relations with the EU was “a much different deal than the people voted on”.
On the subject of a future trade deal, he said the Chequers deal would mean it would be “most likely … we would be dealing with the European Union instead of dealing with the UK, so it will probably kill the deal”.
He said he had told Mrs May how to do a Brexit deal, but: “She didn’t agree, she didn’t listen to me.”
“I told her how to do it. That will be up to her to say. But I told her how to do it. She wanted to go a different route,” he said.
The US president also said he was “cracking down” on the EU because “they have not treated the United States fairly on trading”.
The BBC’s Political Editor, Laura Kuenssberg, said Mr Trump’s interview had “driven a bulldozer” through Mrs May’s claim that the UK would be able to get decent trade deals with the wider world, while sticking to the EU rules.
And Labour MP Phil Wilson, supporter of the People’s Vote campaign which calls for a public vote on the final Brexit deal, said Mr Trump’s comments showed the prime minister’s “botched” Brexit proposal was “worsening hour by hour”.
He said: “She has pinned all her hopes on getting a trade deal with Donald Trump but instead the US president has explicitly backed and strengthened those who advocate a disastrous no deal Brexit.”
Mr Trump’s comments came on the same day the UK government published its proposal for its long-term relationship with the EU.
The long-awaited plan is aimed at ensuring trade co-operation, with no hard border for Northern Ireland, and global trade deals for the UK.