King Charles III will stress the importance of acts of friendship, "especially in a time of need", in an Easter message Thursday that follows his and the Princess of Wales's cancer diagnoses.
The pre-recorded audio comments will be broadcast in his absence at a Maundy Thursday service in Worcester Cathedral in central England, according to Buckingham Palace.
Charles, 75, will say that as a nation, "we need and benefit greatly from those who extend the hand of friendship to us, especially in a time of need".
The comments come after the 75-year-old monarch's daughter-in-law Catherine revealed last Friday in an emotional video message that she was also receiving treatment for cancer.
The king does not refer to his son and heir William's wife in the message.
But royal watchers are likely to interpret his words as a sign of the support that he and the princess have had about their health concerns.
The Maundy Thursday religious service is an annual fixture on the royal calendar and marks the start of the Easter weekend.
Charles will be represented by his wife, Queen Camilla.
Catherine, 42, said in a statement late Saturday that she was "enormously touched by the kind messages" she had received following her shock announcement.
Last month, Charles said he had been reduced to tears by messages and cards of support from well-wishers.
Charles was just 17 months into his reign when the palace announced in early February that he had cancer and would be pausing all public-facing engagements as he commenced treatment.
He is, however, due to attend an Easter Sunday church service this weekend.
He had been admitted for surgery for a benign prostate condition in January but was subsequently diagnosed with an unrelated cancer.
The type of cancer has not been disclosed.
He has been continuing with behind-the-scenes work and holding some in-person meetings and increasingly attending official events.
He praised Kate, as she is widely known, for her bravery by revealing that she was undergoing preventative chemotherapy.
She was last seen at a public engagement on December 25, then underwent abdominal surgery in January, after which cancer was found.
Her Kensington Palace office said at the time that she was not expected to be ready to return to public duties until after Easter. (AFP)
