President Trump called it “highly inappropriate” for his former national security adviser John Bolton to write a memoir about his time in the White House – saying it contained classified information and hinting that Bolton might have lied in the book.

The president’s comments, at a roundtable event at the White House on Monday, followed reports that the Trump administration was expected to take legal action to stop the publication of Bolton’s book.

“Maybe he’s not telling the truth, he’s been known not to tell the truth, a lot,” Trump said Monday.

Sources told Fox News earlier Monday that the White House is expected to make a court filing soon out of the Justice Department to try preventing the publication of Bolton’s memoir slated to be released on June 23, “The Room Where It Happened: A White House Memoir.”

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The White House has long contended that a manuscript of Bolton’s memoir contained classified information, but that the way the material was woven into the narrative would make a traditional “scrub” impossible.

Sources told Fox News the classified information was “part and parcel” of the entire storyline.

The memoir is expected to claim that Trump’s “transgressions” went well beyond the Ukraine saga that led to his impeachment and alleged that “reelection calculations” drove the president’s major decisions, according to a press release for the book.

“This is the book Donald Trump doesn’t want you to read,” the release stated.

“Drawn from his personal participation in key events, and filled with perspective and humor, Bolton covers an array of topics—chaos in the White House, sure, but also assessments of major players, the president’s inconsistent, scattershot decision-making process, and his dealings with allies and enemies alike, from China, Russia, Ukraine, North Korea, Iran, the UK, France and Germany,” the book's publisher said in a statement.

Bolton’s lawyer said last week the publication of the memoir will go ahead as planned on June 23 and he accused the White House of unfairly trying to keep it on ice.

The lawyer, Charles Cooper, wrote in The Wall Street Journal that the White House lawyers have slow-walked the process because “President Trump simply doesn’t want John Bolton to publish his book.”

“This is a transparent attempt to use national security as a pretext to censor Mr. Bolton, in violation of his constitutional right to speak on matters of the utmost public import,” Cooper continued. “This attempt will not succeed, and Mr. Bolton’s book will be published June 23.”

Leaked passages from the manuscript roiled Washington in the midst of Trump’s impeachment trial. Included was the revelation that Bolton said Trump told him he was conditioning the release of military aid to Ukraine on whether Ukraine’s government would help investigate former Vice President Joe Biden and his son Hunter. The younger Biden had been paid by a gas company in Ukraine to serve as a board member.

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Bolton initially submitted the transcript as required to Ellen Knight, the National Security Council’s senior director, for prepublication review of materials written by NSC personnel, on Dec. 30, according to Cooper.

“What followed was perhaps the most extensive and intensive prepublication review in NSC history,” Cooper wrote. “Mr. Bolton and Ms. Knight spent almost four months going through the nearly 500-page manuscript four times, often line by line.”

Cooper said that at the end of the ordeal, Knight told Bolton on April 27, “that’s the last edit I really have to provide for you.”

“Yet when Mr. Bolton asked when he would receive the letter confirming the book was cleared, Ms. Knight cryptically replied that her ‘interaction’ with unnamed others in the White House about the book had ‘been very delicate’ and that there were ‘some internal process considerations to work through,’” Cooper wrote.

Bolton was ousted from his role as national security adviser last September, when the president tweeted that he had fired Bolton, claiming he “disagreed strongly” with his suggestions on a range of issues.

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But, Bolton swiftly challenged Trump’s version of events, telling Fox News he offered to resign after the White House sidelined him from high-level discussions about military involvement in Afghanistan.

Fox News’ John Roberts, Brooke Singman and The Associated Press contributed to this report.