It’s not clear what type of cancer the King, 75, has but officials for Buckingham Palace said it is not prostate cancer, though concerns were raised when the royal underwent a hospital procedure for a benign prostate enlargement. He has since started regular treatments related to his diagnosis.
The King last met Mr Biden, 81, at Windsor Castle in July for the first time since his coronation. The pair reportedly discussed their efforts to address climate change.
While speaking to reporters in Las Vegas, Nevada on Monday at a union event following news of the king’s diagnosis, Mr Biden said, “I’m concerned about him … just heard his diagnosis. But I’ll be talking to him God willing.”
Meanwhile, Mr Trump, who reportedly had a good working relationship with the King during parts of his administration, said, “King Charles has cancer. He is a wonderful man, who I got to know well during my presidency, and we all pray that he has a fast and full recovery.”
The former president posted the message to his social media platform Truth Social.
The King has postponed public-facing duties but will continue to undertake state business and official paperwork.
“He remains wholly positive about his treatment and looks forward to returning to full public duty as soon as possible,” a statement from Buckingham Palace read.
“His majesty has chosen to share his diagnosis to prevent speculation and in the hope it may assist public understanding of all those around the world who are affected by cancer.”
Vedant Patel, a spokesperson for the US Department of State, said the announcement of the King’s diagnosis was “incredibly sad news” during a daily briefing on Monday.
Canadian Prime Minister Justin Trudeau and Israel Prime Minister Benjamin Netanyahu joined the chorus of well wishes on Monday.
“I, like Canadians across the country and people around the world, am thinking of His Majesty King Charles III as he undergoes treatment for cancer,” Mr Trudeau wrote on social media. “We’re sending him our very best wishes – and hoping for a fast and full recovery.”
Mr Netanyahu said: “Sara and I send our heartfelt well wishes to King Charles III and our prayers for his good health.”