"I think she found it maybe too brutal", said the president.
On Friday evening, Trump flew to Scotland where he owns a golf course, ending the formal part of his trip to Britain, but he will not leave Britain for his scheduled meeting with Russian President Vladimir Putin until Sunday.
Speaking at Chequers, Mr Trump told Mrs May "whatever you do is OK with me" on Brexit, but urged her to "make sure we can trade together".
He said the PM "can't walk away" from the talks, but suggested she could use other means to get a good deal.
Asked to rate U.S. -U.K. relations, Mr. Trump gave them the "highest level of special".
New Britain native Manafort transferred to Alexandria jail
Hull said that when jail officials learned Manafort was communicating by email, his attorneys were told to stop the practice. They added that Manafort did not raise questions about his access to his attorneys or documents to prepare his defense.
"We agreed today that as the United Kingdom leaves the European Union we will pursue an ambitious USA -U.K. trade deal", May said Friday at a news conference with Trump at Chequers, her country estate.
Asked about that interview, Trump said he had not criticised May, lavishing praise on "a terrific woman", who was smart, tough and capable.
May's Brexit plan "will definitely affect trade with the United States, unfortunately in a negative way", said the USA president.
Donald Trump claimed he was misquoted by the Sun in his biting criticism of Theresa May - a bombshell for a foreign leader to level while a guest in another country - and said he had the tape to prove it.
He said that May's new, softer approach to Brexit - which would leave Britain sticking to a "common rulebook" with Brussels on goods - would kill off the chances of a much sought-after U.S. -U.K. trade deal.
U.S. officer quits after harassment over Puerto Rico shirt
She said she was thankful officials recognized the behavior of the officer was wrong. Then, she says: "Officer, I'm renting, I paid for a permit for this area".
May's formal proposals were published on Thursday, but hours later the Sun published an interview with Trump where he appeared to side with the prime minister's critics.
However, he later said Ms May was doing a "fantastic job".
New Yorker Ibis Robinson, who has lived in Scotland for years, said she came to stand up against "the hatred and bigotry against anyone who isn't white".
As Mr Trump and Ms May spoke, thousands of protesters marched through central London, one of more than 100 demonstrations against the President planned during his stay.
U.S. ambassador leaves door open to Trump meeting with Johnson
Maybe we'll speak to him when I get over there. "That dream is dying, suffocated by needless self-doubt". Anti-Trump protesters are expected to take to the streets of London during his visit to Britain.
The president later travelled to Windsor Castle for tea with Queen Elizabeth.