President Donald Trump has broken his silence on the news that his niece, Mary Trump, intends to publish a tell-all book about their family.

"She’s not allowed to write a book," the erstwhile Apprentice star told Axios in an interview published on Sunday evening, citing a nondisclosure agreement that she reportedly signed nearly two decades ago.

"You know, when we settled with her and her brother, who I do have a good relationship with — she’s got a brother, Fred, who I do have a good relationship with, but when we settled, she has a total … signed a nondisclosure," Trump continued.

He told the publication that the agreement is a "very powerful one", detailing that "it covers everything".

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Per the president, he and his family were left blindsided last week when details of the book became public.

Trump also said that he has a positive relationship with his niece's brother, who purportedly recently came to visit him at the White House.

"I have a brother, Robert, very good guy, and he’s — he’s very angry about it, but she signed a nondisclosure agreement and she’s obviously not honoring it if she writes a book. It’s too bad," he added.

Watch as Robert De Niro says "lunatic" Trump "doesn't care how many Americans will die" in an impassioned rant:

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"I actually had him — he was in here. He was sitting right in the seat where you are last week, unrelated to that. I didn’t even know — maybe two weeks ago. I didn’t even know about a book coming out until just the other day."

Mary Trump is set to publish the tell-all about the Trump family on the 28th of July. It is titled: Too Much and Never Enough: How My Family Created the World's Most Dangerous Man.

Trump breaks silence on niece's tell-all book