An appeals court judge in New York has lifted a temporary ban on the publication of a potentially explosive "tell-all" book by President Donald Trump's niece, court documents showed.

The ruling issued Wednesday allows publisher Simon & Schuster to print and distribute the 240-page book by Mary Trump, who dubs the US president "the world's most dangerous man."

The president's brother, Robert Trump, had asked for the restraining order, arguing that Mary was violating a non-disclosure agreement signed in 2001 after the settlement over the estate of Fred Trump -- the father of Donald and Robert and of Mary's father Fred Trump Jr.

Judge Alan Scheinkman postponed addressing whether the author had violated the non-disclosure agreement preventing her from revealing family secrets by writing the book, titled "Too Much and Never Enough: How My Family Created the World's Most Dangerous Man."

Nevertheless, Simon & Schuster "is not a party to the agreement," so the block of their publication of the book "is vacated," he ruled.

In a statement, Mary Trump's attorney Ted Boutrous said the lifting of the prior restraint against the publisher was "very good news."  

"We look forward to filing our brief tomorrow (Thursday) in the trial court explaining why the same result is required as to Ms Trump, based on the First Amendment and basic contract law," he said.

Mary Trump's legal team said they were hoping for a July 10 hearing, which will most likely take place virtually.

In the book, Mary, a clinical psychologist, recounts what she witnessed of the "toxic family" in the home of her grandparents, according to her publisher.

The Daily Beast reported earlier that the book will reveal that Mary Trump was the crucial source for explosive New York Times reporting on Trump's finances, which suggested the billionaire paid little in tax for decades.