The Duke of Edinburgh will miss a church service attended by members of the royal family, as his stay in hospital enters its fifth day.
The Queen is among those expected to attend the service at Crathie Kirk, near Balmoral, on Sunday.
But Philip, 91, continues to receive treatment for a flare-up of a bladder infection at Aberdeen Royal Infirmary.
The Duke has so far not received any visits from his relatives after doctors advised him to rest on Friday.
He was admitted to the NHS hospital on Wednesday, during his and the Queen's annual summer break at Balmoral.
Officials said at the time that he would be in the infirmary for a few days and it remains unclear when he will be discharged.
He is said to have been in regular contact with members of his family by telephone.
Buckingham Palace did not issue any updates on the Duke's condition on Saturday, although he was previously said to be responding well to treatment for the recurrence of the infection he suffered in the summer.
It is not yet known whether he will attend his next official engagement — accompanying the Queen to the opening of the London 2012 Paralympic Games on August 29.