Donald Trump has said that Americans "are praying" for Boris Johnson after the British prime minister was moved to an intensive care ward after his Covid-19 symptoms worsened.

Appearing at his daily White House briefing on the coronavirus, the president said: "I also want to send my best wishes to a very good friend of mine and a friend to our nation, Prime Minister Boris Johnson.

"We're very saddened to hear that he was taken into intensive care this afternoon, a little while ago.

"And Americans are all praying for his recovery. He's been a really good friend, he's been really something very special: strong, resolute, doesn't quit, doesn't give up."

He called Mr Johnson a "warm guy" who "really loves his country".

"Intensive care is big stuff," he said.

Asked if he or vice president Mike Pence would reconsider their own behaviour in light of the prime minister's worsening illness, he said they might get more coronavirus tests. Both have tested negative in previous tests.

The president said he had told two "genius" companies to get in touch with the prime minister's doctors although it was not immediately clear what they would be offering.

Mr Trump said: "We've contacted all of Boris's doctors, and we'll see what is going to take place. But they are ready to go. But when you get brought into intensive care, it gets very serious with this particular disease."

He added: "It's a very complex treatment of things that they've just recently developed. They've already had meetings with the doctors, and we'll see whether or not they want to go that route."

Asked about Mr Johnson's relatively late decision to create an effective lockdown in the UK, the president said "many people were thinking about riding it out, meaning, whatever it is, it is" and said countries acted once the numbers of cases and deaths became "monumental".

He said the US "actually moved early" with its travel bans from China and Europe.

Mr Trump added that the prime minister "made a decision very quickly thereafter to do what they did" but the UK is "suffering greatly as a nation right now".

Of the United Kingdom, he said: "They're suffering a lot, they're a nation that's having a difficult time."