King Charles III is reportedly frustrated by Prince Harry’s reaction to losing his security appeal — including a public claim the king “won’t speak” to him.

Prior to Harry’s bombshell BBC News interview on Friday, a friend of King Charles said it would have been “constitutionally improper” for the monarch to become involved in the appeal, which would have restored publicly funded security to the Duke of Sussex.

“What has frustrated and upset him on a more personal level is the Duke’s failure to respect this principle,” the insider told The Sun. “And for his supporters to suggest that somehow his father doesn’t care about his family, or should step in.”

“He’s been particularly concerned that it has taken considerable resources and cost for the Government to defend their position,” the insider added.

A palace spokesperson also defended the outcome of the appeal in a statement: “All of these issues have been examined repeatedly and meticulously by the courts, with the same conclusion reached on each occasion.”

The king’s frustration comes after Harry, 40, sat down with the BBC for a surprise interview, in which he claimed “some members” of the royal family will “never forgive” him for a number of alleged offenses — among them, writing his 2023 memoir, “Spare.”

Despite the ongoing “differences” the Duke of Sussex has with his family, the father or two said “there’s no point in continuing to fight” and that he would “love reconciliation” — especially given that he doesn’t “know how much longer” his father, 76, will live after receiving his cancer diagnosis in early 2024.

“He won’t speak to me because of this security stuff,” Harry told the news outlet. “But it would be nice to reconcile.”

Harry — who stepped away from his royal duties and relocated to California in 2020 — added that if the royal family members “don’t want that,” then it’s “entirely up to them.”

Regardless, he doesn’t expect to bring his children — Prince Archie, 6, and Princess Lilibet, 3 — and wife Meghan Markle back to his home country anytime soon.

“I can’t see a world in which I would be bringing my wife and children back to the UK at this point,” he continued. “And the things that they’re gonna miss is, well, everything.”

Of the security court case, the prince said “the whole thing could be resolved through [Charles].”

“Not necessarily by intervening, but by stepping aside, allowing the experts to do what is necessary,” he said.

Notwithstanding, Harry said he loves his home country “despite what some people in that country have done.”