The King has apologised for having to postpone engagements after his cancer diagnosis.
Buckingham Palace said the diagnosis means his forthcoming public engagements will have to be rearranged or postponed, as the Queen continues to attend to a full programme of public duties.
The service is usually attended by senior members of the Royal Family.
It was also expected the King and Queen would have several high-profile overseas visits over the coming months.
Buckingham Palace is yet to confirm whether the tours – his first visits to those countries as King – will go ahead.
No date has been suggested for the King’s return to full public duties as he undergoes treatment.
The Palace has not officially confirmed any upcoming state visits.
“Regrettably, a number of The King’s forthcoming public engagements will have to be rearranged or postponed,” a Palace spokesperson said.
“His Majesty would like to apologise to all those who may be disappointed or inconvenienced as a consequence.”
It is understood the King will continue to receive red boxes and have weekly audiences with the prime minister while undergoing treatment.
It is expected that alternative arrangements will be put in place for the weekly audiences should the King be advised by doctors to minimise in-person contact.