World leaders and politicians from across the spectrum have rallied to support Prime Minister Boris Johnson, who is in intensive care.
Johnson was diagnosed with coronavirus 11 days ago, but his condition has worsened in the last 24 hours.
He was taken to hospital in London on Sunday night and on Monday evening was moved into intensive care.
Buckingham Palace said the Queen was being “kept informed” about Johnson’s condition.
At a White House press conference, US President Donald Trump said: “Before I begin, I want to express our nation’s well wishes to Prime Minister Boris Johnson as he wages his own personal fight with the virus.
“All Americans are praying for him. He’s a friend of mine. He’s a great gentleman and a great leader, and as you know he was brought to the hospital today, but I’m hopeful and sure that he’s going to be fine.
“He’s a strong man, a strong person.”
His predecessor at 10 Downing Street, Theresa May, said: “My thoughts and prayers are with Boris Johnson and his family as he continues to receive treatment in hospital.”
World leaders shared their thoughts on social media, with French president Emmanuel Macron saying: “All my support for Boris Johnson, his family and the British people at this difficult time. I wish him to overcome this ordeal quickly.”
Canada’s prime minister Justin Trudeau said: “Sending my best wishes to for a full and speedy recovery. My thoughts are with you and your family right now. Hope to see you back at Number 10 soon.”
The EU’s chief Brexit negotiator Michel Barner said: “Wishing Boris Johnson all the best and a speedy recovery. My thoughts are with you and your family.”
Indian prime minister Narendra Modi said: “Hang in there Prime Minister Boris Johnson. Hope to see you out of hospital and in perfect health very soon.”
Nato secretary general Jens Stoltenberg added: “My thoughts are with my friend Boris Johnson. Lots of strength, Boris, and get well soon.”
President Donald Trump’s daughter Ivanka said: “My thoughts and prayers are with Boris Johnson and his family.”
Leaders of UK parties also reacted on social media to the news, which broke shortly after 8pm.
Scotland’s First Minister Nicola Sturgeon said her thoughts were with the Prime Minister’s family.
And newly elected Labour leader Keir Starmer said it was “terribly sad”, adding: “All the country’s thoughts are with the Prime Minister and his family during this incredibly difficult time.”