LONDON (AP) — King Charles III and Queen Camilla will attend an Easter service at the chapel at Windsor Castle on Sunday, Buckingham Palace officials said Tuesday, in the first major appearance for the 75-year-old king since he was

diagnosed with cancer

in February.

Officials said Charles and Camilla will be accompanied by members of the royal family at St. George's Chapel. The event is expected to be smaller than usual. Prince William and

Kate, the Princess of Wales

, who announced last week that she is also undergoing cancer treatment, are not expected to attend.

The king is undergoing treatment and has suspended almost all his public engagements since his diagnosis. Officials didn’t disclose what form of cancer Charles has but said it’s not related to his

recent treatment

for a benign prostate condition.

Officials have said the monarch is continuing with state business, including regular weekly meetings with Prime Minister Rishi Sunak, and won't be handing over his constitutional role as head of state.

On Tuesday, Charles was shown meeting community and faith leaders from across the U.K. at Buckingham Palace to hear about their work of boosting social cohesion amid heightened international tensions.