Catherine, Princess of Wales, announced on Friday she will make her first public appearance in six months this weekend after "making good progress" in treatment for cancer.

The 42-year-old future queen will attend King Charles III's annual birthday parade on Saturday with other senior royals, which the British monarch is participating in despite his own cancer battle.

Kate, as she is widely known, said in a statement she was "not out of the woods yet" but that she hoped to join in "a few public engagements over the summer" months.

"I am making good progress, but as anyone going through chemotherapy will know, there are good days and bad days," she said, adding treatment for the unspecified cancer would continue "for a few more months".

"On those bad days you feel weak, tired and you have to give in to your body resting. But on the good days, when you feel stronger, you want to make the most of feeling well."

Kate, married to heir-to-the-throne Prince William and mother to their three young children, noted that she has started to do "a little work from home" on days when she "feels well enough".

'Time to heal'

"It is a joy to engage with school life, spend personal time on the things that give me energy and positivity," she added.

"I'm looking forward to attending the King's birthday parade this weekend with my family and hope to join a few public engagements over the summer, but equally knowing I am not out of the woods yet."

The statement, first released on Kate's social media channels, was accompanied by a photograph -- taken earlier this week in Windsor, west of London -- of the princess standing in front of a tree next to a river.

"I am learning how to be patient, especially with uncertainty. Taking each day as it comes, listening to my body, and allowing myself to take this much-needed time to heal," she added.

The princess thanked people for their "continued understanding" and those who had "so bravely shared your stories with me".

The popular royal revealed she had been "blown away by all the kind messages of support and encouragement" received since revealing the diagnosis in March.

Her appearance at Saturday's annual Trooping the Colour parade for Charles's official birthday will be her first public appearance since she was seen gathering with other royals for Christmas last December.

Kate announced in a video almost three months ago that she had been diagnosed with cancer discovered following abdominal surgery, triggering a wave of support from global leaders, family members, media and the public. 

Parade

Charles, 75, had only weeks earlier revealed he was being treated for an unspecified cancer, leaving the British monarchy in crisis with two of its most senior members simultaneously fighting serious illness. 

Charles was just 17 months into his long-awaited reign when Buckingham Palace announced in early February that he would be pausing all public-facing engagements as he commenced treatment.

He had undergone 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 continued with behind-the-scenes work and holding some in-person meetings and in April royal officials said doctors were "very encouraged" by his progress, allowing him to resume his official duties.

However, he will participate in this year's birthday parade from a carriage, rather than on horseback as he did at his inaugural parade as king last year.

It was the first time the monarch had ridden at it since his mother, Queen Elizabeth II, in 1986.

The yearly event marks the sovereign's official birthday and is one of the highlights of the royal calendar.