The trip is said to be a solo one, with the Duchess of Sussex staying in the US with the couple’s two children, Prince Archie and Princess Lilibet, according to the MailOnline.
Buckingham Palace confirmed the disease, which is not prostate cancer, was discovered while the King was being treated in hospital for an enlarged prostate.
Charles told Harry and Prince William of his diagnosis personally.
"The duke did speak with his father about his diagnosis. He will be travelling to UK to see His Majesty in the coming days," the Office of The Duke and Duchess of Sussex said on Monday.
The decision will also raise hopes of a reconciliation within the royal family.
Harry has a troubled relationship with his father, although they are still in contact, but his long-running rift with the Prince of Wales remains ongoing.
Charles, according to Harry, pleaded with his sons during a tense meeting after the Duke of Edinburgh's funeral: "Please, boys. Don't make my final years a misery."
Harry and Meghan wanted a half in-half out approach to royal life, but in the end quit as senior working royals amid the Megxit crisis in 2020.
The King has started a schedule of regular treatments, but has been advised to postpone his public-facing duties.
The Palace declined to confirm the type of cancer.
Charles will carry on working behind the scenes on state business and official papers, and returned from Sandringham to London on Monday to commence treatment as an out-patient.
Buckingham Palace said in a statement: “During The King’s recent hospital procedure for benign prostate enlargement, a separate issue of concern was noted.
“Subsequent diagnostic tests have identified a form of cancer.
“His Majesty has today commenced a schedule of regular treatments, during which time he has been advised by doctors to postpone public-facing duties.
“Throughout this period, His Majesty will continue to undertake State business and official paperwork as usual.
“The King is grateful to his medical team for their swift intervention, which was made possible thanks to his recent hospital procedure.
“He remains wholly positive about his treatment and looks forward to returning to full public duty as soon as possible.
“His Majesty has chosen to share his diagnosis to prevent speculation and in the hope it may assist public understanding for all those around the world who are affected by cancer.”
Charles, 75, was discharged from the London Clinic a week ago after undergoing treatment on an enlarged prostate.
The shock news is the latest health scare to hit the royal family at the start of 2024, coming after the King’s hospital stay, the Princess of Wales’s major abdominal surgery and Sarah, Duchess of York’s diagnosis of skin cancer.
Buckingham Palace announced on January 16 that the King was to have treatment for an enlarged prostate, but that the condition was benign.
The Palace announced the King’s cancer diagnosis at 6pm on Monday.
Charles, who acceded to the throne just 17 months ago, was last seen on Sunday when he attended church in Sandringham.