Donald Trump backed Boris Johnson to win next week's general election – but insisted he “could work with anybody”, including Jeremy Corbyn .
"I think Boris is very capable and I think he'll do a good job," the US President said.
Asked if he could work with Labour leader during an impromptu press conference, Mr Trump said: "I can work with anybody, I'm a very easy person to work with.”
But of Mr Corbyn, he added: “I know nothing about the gentleman.
"Really, Jeremy Corbyn. Know nothing about him."
President Trump is visiting the UK for a NATO summit to celebrate 70 years of the organisation.
Despite claiming to know nothing about Mr Corbyn, the US President has made comments about him in the past.
In October, he told Nigel Farage on LBC: "Corbyn would be so bad for your country, he'd take you into such bad places."
In August, he tweeted: "Would be very hard for Jeremy Corbyn, the leader of Britain’s Labour Party, to seek a no-confidence vote against New Prime Minister Boris Johnson , especially in light of the fact that Boris is exactly what the U.K. has been looking for, & will prove to be “a great one!” Love U.K."
And in June, he claimed it would have been "inappropriate" to meet with him during his visit to London - despite meeting with several senior Tories and Nigel Farage.
President Trump also briefly touched on the row over the death of Harry Dunn, the British teenager killed when his motorbike crashed into a car outside RAF Croughton in Northamptonshire on August 27.
American Anne Sacoolas, the 42-year-old motorist allegedly responsible for the crash, claimed diplomatic immunity and was allowed to return to the US. Harry's family's spokesman said they would be "congregating outside Buckingham Palace" to make "our presence known".
Mr Trump said Harry's parents were "lovely people", adding: "We're trying to work something out."
The US President spent the day rattling the tin for his White House re-election campaign, pressing be donors to pump cash into his election war chest.
He was holding an event in London for mega-rich US citizens aimed at raising $3million for his fight. An invitation, seen by US news website Axios, listed three levels of donor.
Those giving $125,000 and above were invited to join a roundtable meeting, have their photo taken with the President and attend a reception.
A donation of at least $35,000 was required to attend the reception, and $50,000 was the minimum to have a photo taken.
