Prince Harry makes an explosive claim in his new memoir "Spare" that his older brother Prince William physically attacked him in a confrontation over Harry's wife Meghan, the Duchess of Sussex, according to a report in The Guardian.

The U.K. newspaper claims in an article published late Wednesday that it obtained an advance copy of "Spare," scheduled to be released Jan. 10.

According to The Guardian, Harry writes in his memoir that during a 2019 conversation in his Nottingham Cottage home, William called Meghan, whom Harry had wed the year before, "difficult," "rude" and "abrasive."

Harry writes, according to The Guardian, that William went on to say that he was trying to help, to which Harry responded, "Are you serious? Help me? Sorry – is that what you call this? Helping me?”

Harry says he then walked into the kitchen, with William following him, and gave his brother a glass of water, saying, "Willy, I can't speak to you when you're like this," according to The Guardian's reporting.

“He set down the water, called me another name, then came at me. It all happened so fast. So very fast. He grabbed me by the collar, ripping my necklace, and he knocked me to the floor," Harry writes in "Spare," per The Guardian. "I landed on the dog’s bowl, which cracked under my back, the pieces cutting into me. I lay there for a moment, dazed, then got to my feet and told him to get out.”

Harry writes that he didn't initially tell Meghan about the incident but later did when she saw "scrapes and bruises" on his back. Her reaction, according to Harry, was that she was "terribly sad," according to The Guardian.

Buckingham Palace and Kensington Palace declined ABC News' request for comment on the alleged altercation.

In a new interview airing Monday on "Good Morning America," Harry speaks in-depth to "GMA" co-anchor Michael Strahan about his relationship with William.

"There has always been this competition between us," said Harry, who describes William in his memoir as his "beloved brother and arch nemesis." "It really plays into, or is played by, the heir/spare.”

The memoir's title, "Spare," is a nod to Harry's birth order as the younger brother of William, the heir to the throne. Harry is fifth in line to the throne, behind William and William's three children.

Watch Michael Strahan's interview with Prince Harry on Monday, Jan. 9 at 7 a.m. EST on "Good Morning America" and the special, “Prince Harry: In His Own Words | Michael Strahan Reporting” later on ABC News Live.

In the new interview with Strahan, Harry also discusses the current state of his relationship with his father King Charles III as well as how he thinks his mother, the late Princess Diana, would react to the rift between her sons.

The release of Harry's highly anticipated memoir comes just weeks after Harry and Meghan's closely followed docuseries aired on Netflix and broke records as the platform's biggest documentary debut ever.

Harry said previously that the memoir would be a "firsthand account of my life that's accurate and wholly truthful."

The memoir is said to cover everything from Harry's experience growing up in the royal family to his time in the military, the death of his mother, his decision in 2020 to step down from his role as a senior working royal and his life now as a husband and father.

Watch Michael Strahan's interview with Prince Harry on Monday, Jan. 9, at 7 a.m. EST on "Good Morning America" and the special, "Prince Harry: In His Own Words | Michael Strahan Reporting" at 8:30 p.m. EST on ABC News Live.