US President Donald Trump says the UK is in "turmoil" and it is "up to the people" whether or not Theresa May remains as prime minister.
Speaking as he prepared to depart for a European trip in which he will meet May at the NATO summit in Brussels and then make his first visit to the UK as president, Trump insisted he got along with May "very well".
But he suggested that he might take time during his UK visit to speak with former foreign secretary Boris Johnson, who he described as "a friend of mine".
Speaking on the lawn of the White House as he and his wife Melania prepared to board the Marine One presidential helicopter, Mr Trump said that the UK "certainly has a lot of things going on".
"It's going to be an interesting time in the UK and an interesting time at NATO," he said. "We will work it out and all countries will be happy.
"So I have NATO, I have the UK - which is in somewhat turmoil."
Referring to Monday's planned summit with Russian president Vladimir Putin in Helsinki, Trump added: "And I have Putin. Frankly, Putin may be the easiest of all."
Trump wouldn't say whether he considered Putin a friend or foe, calling him only a "competitor."
Asked whether May should be replaced as prime minister, the US president replied: "Well that's up to the people. I get along with her very well, I have a very good relationship. That's certainly up to the people, not up to me."
Trump said he had not spoken with May, adding: "Boris Johnson is a friend of mine. He's been very, very nice to me, very supportive. Maybe I'll speak to him when I get over there.
"I like Boris Johnson, I've always liked him."
Trump repeated his demands for the EU to lower barriers to US imports and for America's NATO allies to pay more towards their own defence.
"We do have a lot of allies, but we can't be taken advantage of," he said. "We are being taken advantage of by the EU."
In response, European Council President Donald Tusk told Trump to stop berating NATO allies.
"Dear America, appreciate your allies, after all you don't have that many," Tusk said after signing a statement on more cooperation between the European Union and NATO, although he also accepted Europe should spend more on defence.
"Dear President Trump: America does not have, and will not have a better ally than Europe.
"Today, Europeans (collectively) spend on defence many times more than Russia, and as much as China."