- Peter Phillips gave an update on King Charles' cancer during an interview with Sky News Australia.
- Phillips said his uncle was "frustrated" that his cancer and treatment were preventing him from working.
King Charles is impatient to get back to work amid his cancer treatment, a royal family member has said.
Peter Phillips, 46, is the eldest son of Princess Anne and Mark Phillips. The king's nephew was Queen Elizabeth II and Prince Philip's first grandchild.
On Sunday, Phillips appeared on Sky News Australia's Royal Report while visiting the country to support the charity ISPS Handa.
During his interview, Phillips, who's 18th in line for the throne, briefly discussed the king's health, telling the host Caroline Di Russo that Charles was "in good spirits" but "frustrated."
"I think, ultimately, he's hugely frustrated," Phillips said. "He's frustrated that he can't get on and do everything that he wants to be able to do."
"But he is very pragmatic," he said of the king. "He understands that there's a period of time that he really needs to focus on himself. But at the same time, he is always pushing his staff and everybody and his doctors and nurses to be able to say, actually, you know, can I do this? Can I do that?"
On February 5, Buckingham Palace announced in a statement shared with Business Insider that the king had been diagnosed with an unspecified type of cancer.
The palace said the king started a "schedule of regular treatments" that day, adding that his medical team advised him to pause his "public-facing duties" while he undergoes treatment.
The king has largely been absent from the public eye since the announcement, though he has held some meetings at Buckingham Palace and been photographed a handful of times since February.
Charles has also been supportive of Kate Middleton, who disclosed on Friday that she'd been undergoing preventive chemotherapy after being diagnosed with an undisclosed form of cancer. A Buckingham Palace spokesperson said the king had "remained in the closest contact with his beloved daughter-in-law throughout the past weeks."
Buckingham Palace has not yet announced when the king will return to his public-facing duties.