(CNN) — President Donald Trump said that his niece, who is set to publish a tell-all book about him and his family, had signed a nondisclosure agreement and is “not allowed to write a book.”

Mary Trump, the daughter of the president’s late brother, Fred Trump Jr., has  written a book described as a “revelatory, authoritative portrait of Donald J. Trump and the toxic family that made him.” The book is set to be released on July 28, according to its publisher, Simon & Schuster.

“She’s not allowed to write a book,” Trump told Axios in an interview Friday. “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.”

Simon & Schuster declined to comment Sunday evening. CNN had previously reached out to Mary Trump for comment.

Trump has dealt with several unflattering portrayals of his presidency written by former staffers, including a soon-to-be published book by former national security adviser John Bolton. Mary Trump’s book is the first from a family member that criticizes the president.

The Daily Beast first reported on Mary Trump’s book, “Too Much And Never Enough,” and said she had signed a nondisclosure agreement following a 2001 settlement of litigation over Fred Trump Sr.’s estate.

Mary Trump and Fred Trump III had contested the will of their grandfather, which reportedly gave them smaller bequests than those of their cousins.

Citing people with knowledge of the matter, the Daily Beast reported that Mary Trump reveals in her book that she was a primary source for The New York Times‘ 2018 investigation that found Trump helped “his parents dodge taxes” in the 1990s, including “instances of outright fraud” that allowed him to amass a fortune from them.

The president has not read his niece’s upcoming book, White House press secretary Kayleigh McEnany said Friday.

According to the book’s description, Mary Trump recounts how her uncle “dismissed and derided” his father, Fred Trump Sr., “when he began to succumb to Alzheimer’s.”

The president called the allegation “totally false” in his interview with Axios.

“It’s totally false; the opposite,” he said. “Actually, the opposite. I always had a great relationship. I didn’t know that she said that. That’s a disgraceful thing to say.”

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