WASHINGTON - The publisher of a book that questions President Trump's fitness for office said any effort by Mr. Trump to suppress the book would be "flagrantly unconstitutional."

Henry Holt

In a letter to company employees Monday and shared with CBS News, Macmillan CEO John Sargent wrote "no American court" would go along with President Trump should he sue to have "Fire and Fury: Inside the Trump White House", withdrawn.

"The president is free to call news "fake" and to blast the media," Sargent wrote. "But a demand to cease and desist publication - a clear effort by the President of the United States to intimidate a publisher into halting publication of an important book on the workings of the government - is an attempt to achieve what is called prior restraint."

Macmillan is the parent organization of Henry Holt and Company, which released the book, by author Michael Wolff. A Trump lawyer last week sent a cease and desist letter to the publisher, demanding it be withheld. Holt responded by moving up the release date from Jan. 9 to last Friday.

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In the letter released to employees Monday, Sargent said that the company would send a formal response to Trump later in the day.

Wolff's book portrays the 45th president as a leader who doesn't understand the weight of his office and whose competence is questioned by aides.

Former Trump Campaign CEO and White House Chief Strategist Steve Bannon was widely quoted. In one instance, he describes a meeting between Donald Trump Jr., senior campaign aides and a Russian lawyer as "treasonous" and "unpatriotic". The reference angered the president, who last week said Bannon "lost his mind."

Over the weekend, the president's allies attacked the book in a round of television appearances Sunday. Chief policy adviser Stephen Miller, in a combative appearance Sunday on CNN, described the book as "nothing but a pile of trash through and through." While the president countered the book's claims by tweeting that he is a "stable genius," and said "Fire and Fury" is a "fake book."

Wolff responded on "CBS This Morning," saying "everything in the book is true." He also addressed the president's claim that he never spoke with the author for the book.

"I think he probably had no idea he was speaking to me for this book. When I would meet the president in the White House, we would chat as though we were friends," Wolff said. "I have sat down with the president for extended periods of interviews. But there are other periods -- and that's essentially what he's saying. They're trying to parse this, saying, 'Oh, I didn't know I was speaking to him when I saw him in the White House.'"