Trump says his niece Mary can't publish a tell-all because she signed a 'very powerful' NDA — and says his family was blindsided by the book

• President Donald Trump's niece, Mary Trump, is preparing to publish a book about her family and the man she describes as her "dangerous" uncle.
• Her book is scheduled to publish July 28. The publisher Simon & Schuster says it will be a "revelatory, authoritative portrait of Donald J. Trump and the toxic family that made him."
• The president commented on reports of the book in an interview with Axios, published Sunday, saying Mary was "not allowed to write a book" because she signed a nondisclosure agreement with the family.
• He also said some members of his family were blindsided by the book, and he forcefully denied a specific claim involving his relationship with his father.

President Donald Trump addressed his niece's coming tell-all for the first time in an interview with Axios.

The president told the outlet, in an interview published Sunday, that his niece, Mary Trump, was "not allowed" to publish a book because she had signed a nondisclosure agreement.

He also said the book had taken members of their family by surprise, and he contested one of the book's claims.

"She's not allowed to write a book," Trump told Axios' Jonathan Swan, adding that she "signed a nondisclosure" when he settled a lawsuit brought on by her and her brother, Fred Trump III.

The settlement Trump was referring to was an issue over his father's estate.

Mary's father, Fred Trump Jr., died at the age of 42 in 1981 because of alcoholism. When Fred Trump died in 1999, Mary Trump and Fred Trump III contested the will, saying they should have received what would have been their father's share of the will had he outlived his father.

The case was settled privately.

Donald Trump said the nondisclosure agreement was a "very powerful one" and "covers everything."

The Daily Beast reported last week that Trump had told his inner circle that he's having his lawyers look into what they could do to legally threaten his niece over the book.

The president said he's not the only member of his family shocked to learn his niece was planning a tell-all about him. He said his younger brother, Robert, was "very angry about it" as well.

Trump also said he had a "good relationship" with Mary's brother, saying he had him to the White House just last week for an unrelated reason.

The publisher Simon & Schuster has released a statement describing "Too Much and Never Enough" as a "revelatory, authoritative portrait of Donald J. Trump and the toxic family that made him."

As a clinical psychologist, "Mary L. Trump has the education, insight, and intimate familiarity needed to reveal what makes Donald, and the rest of her clan, tick," Simon & Schuster said.

The book will detail claims that Trump "dismissed and derided" his own father when the elder Trump started succumbing to Alzheimer's in the 1990s, according to Simon & Schuster.

The president contradicted this claim in his interview with Axios, saying "it's totally false" and was "actually the opposite."

"I didn't know that she said that," Trump said. "That's a disgraceful thing to say."

Simon & Schuster and the White House did not immediately respond to Business Insider's requests for comment.

The book, scheduled to publish July 28, is No. 4 on the Amazon best-seller list for books.

Earlier this month, the Trump administration sued Trump's former national security adviser John Bolton over his coming book, alleging that the book contains classified information.

• Read more:
• Everything we know about Mary Trump, the president's niece who is a life coach, apparent Hillary Clinton fan, and is publishing a scathing tell-all about her uncle
• Trump is reportedly looking into suing his niece to stop her from publishing a tell-all book about him
• How Trump uses money, non-disclosure agreements, and intimidation to muzzle the people close to him
• Trump's niece is publishing a tell-all book that says she leaked tax documents to help The New York Times investigate the president's finances