The prime minister will have his weekly audience with the King over the phone following the monarch's cancer diagnosis, Downing Street has said.
The private meeting is normally held in person in Buckingham Palace.
"We don't in general - and we are not going to - get into the habit of commenting on the PM's conversations with the King," said Rishi Sunak's spokesman.
"But we have agreed with the Palace in this specific instance to confirm that they will be speaking on the phone later."
The spokesman did not say whether the arrangement is a one-off or if it will continue during the King's treatment.
The meeting is held to discuss government matters, but details are not released and it's an established principle that the monarch remains neutral on political issues.
However, he's able to "advise and warn" the prime minister when necessary.
"I know the thoughts of the House and the country are with the King and his family," said Mr Sunak.
"We wish His Majesty a speedy recovery and look forward to him resuming his public-facing duties in due course."
The King was yesterday seen in public for the first time since he revealed his cancer diagnosis.
He was driven from Clarence House to the Palace and then took a helicopter to the Sandringham estate in Norfolk.
Prince Harry also arrived in the UK from California and had a short meeting with his father - but on Wednesday afternoon was seen back at Heathrow.
The King revealed his cancer diagnosis on Monday but the Palace has not revealed what form of the disease he has.
It was identified during his recent treatment for an enlarged prostate - but is not prostate cancer.
The Palace said the King would "continue to undertake state business and official paperwork as usual" as he undergoes treatment but that "public-facing duties" have been postponed.
Prince William returned to duties on Wednesday at an investiture ceremony at Windsor and will later attend a gala dinner for the London Air Ambulance.
It was also the first time he has been at a royal event since his wife's abdominal surgery.
Kate and her father-in-law were both treated at the same private London hospital.
Other members of the Royal Family, such as Princess Anne and Prince Edward, are also expected to take on extra duties in the weeks ahead as the King steps back.