Melania Trump's spokesperson did not immediately respond to a request for comment.
However as he arrived for a working lunch with the British prime minister he said they had "probably never developed a better relationship" than during last night's dinner at Blenheim Palace. "I think they like me in the UK".
"I think he's got what it takes, and I think he's got the right attitude to be a great prime minister".
Trump also said former foreign minister Boris Johnson, who resigned this week in protest over the plan, would make "a great prime minister".
May has defended the plan, saying it delivers "on the vote of the British people to take back control of our money, our laws and our borders".
Trump went on: "You have a mayor who has done a awful job in London".
"I believe that the people in the UK - Scotland, Ireland, as you know I have property in Ireland, I have property all over - I think that those people they like me a lot and they agree with me on immigration". The first lady will remain in London on Friday when protests are set to take place. "As he said in his interview with The Sun she "is a very good person" and he 'never said anything bad about her.' He thought she was great on North Atlantic Treaty Organisation today and is a really terrific person".
Hurricane Chris to bring rain to the United Kingdom next week
Atlantic Canada residents are being warned these conditions could cause life-threatening surf and rip current conditions . Stormy conditions are expected to taper off through the overnight hours as Chris continues to push northeast.
It comes just days after Trump declined to say whether May should remain in post, said he had "always liked" Boris Johnson, who quit as foreign secretary over the Chequers agreement, and described the United Kingdom as being in "turmoil".
His criticism of Britain's anti-terror policies after a series of attacks in 2017 also did not go down well. So naturally, they have insisted we bring Trump Baby up from London to fly over his golf course, in solidarity with their struggle against Trump's hateful politics.
In the Sun interview, which was conducted during Wednesday's North Atlantic Treaty Organisation summit in Brussels, Trump renewed attacks on Mayor of London Sadiq Khan, with whom he has a long-running feud.
United States political website The Hill also focused on Mr Trump's comments about "millions and millions of people" coming to Europe from the Middle East and Africa.
Melania Trump will arrive in England from Brussels today with Donald Trump ahead of a visit which will be marked by protests, a "Go Home" van driving around Westminster - and a six-metre tall orange inflatable baby.
Trump told The Sun newspaper on Thursday - in an interview that was published as he was being feted by May at an opulent dinner at a country palace - that he felt unwelcome in London because of protests, including plans to fly a giant balloon over Parliament on Friday that depicts him as an angry baby in a diaper.
During that visit, tens of thousands of people joined a demonstration in central London that culminated in a rally in Trafalgar Square, at which an effigy of Bush was toppled from a plinth.
While Trump's trip was not the full state visit he was originally promised, he was heralded by military bands on his arrival in the country and at Blenheim, and he is scheduled on Friday to have tea with Queen Elizabeth.