A lawyer for President Donald Trump sent a cease-and-desist letter to Steve Bannon on Wednesday after the former White House chief strategists incendiary comments about the Trump presidency were revealed in a forthcoming book.

ABC News was the first to obtain the letter in which attorney Charles Harder said Bannon broke the terms of a confidentiality and non-disparagement agreement he had signed when he joined Trumps presidential campaign in August 2016.

Bannon had breached the Agreement by, among other things, communicating with author Michael Wolff about Mr. Trump, his family members, and the Company [the campaign], disclosing Confidential Information to Mr. Wolff, and making disparaging statements and in some cases outright defamatory statements to Mr. Wolff about Mr. Trump, his family members.

Harder confirmed to HuffPost on Wednesday evening that the letter had been sent to Bannon.

In a statement provided to ABC, Harder said Bannons comments for the book give rise to numerous legal claims including defamation by libel and slander. He said legal action was imminent.

Bannons explosive claims were first reported by The Guardian on Wednesday after the outlet obtained a review copy of Michael Wolffs book Fire and Fury: Inside the Trump White House, set to be released Tuesday. In interviews with Wolff, Bannon suggested that Trump was aware of a meeting his son Donald Trump Jr. had with Russian operatives at Trump Tower in June 2016 and that the then-candidate met with the delegation himself. Bannon also described the meeting as treasonous and bad shit.

Even if you thought that this was not treasonous, or unpatriotic, or bad shit, and I happen to think its all of that, you should have called the FBI immediately, Bannon told Wolff, according to The Guardian.

Trump unleashed a furious denial of Bannons claims on Wednesday, saying his former adviser had lost his mind and alleging the former campaign chief had very little to do with our historic victory.

Steve Bannon has nothing to do with me or my Presidency, Trump said in a statement, which also accused Bannon of leaking information to the media. When he was fired, he not only lost his job, he lost his mind.

Harders letter sent Wednesday also said Bannon could be liable for monetary damages.