The Department of Justice is asking for information that could help it identify the anonymous author behind a forthcoming book that has been billed as an "unprecedented behind-the-scenes portrait" of President Donald Trump's time in office.

Assistant attorney general Joseph Hunt sent a letter on Monday to the author's publisher and literary agency demanding assurances that the author, who claims to be a current or former senior official in the Trump administration, did not sign a nondisclosure agreement and "did not have access to any classified information in connection with government service."

If the two firms, Hachette Book Group and Javelin, could not provide such a guarantee, Hunt asked them to provide the anonymous author's dates of government service and the agencies where the author was employed.

The government could likely use those details to determine the author's identity. The book, titled "A Warning," is scheduled to go on sale Nov. 19.

Hachette and Javelin responded defiantly later in the day, declining to comply with the Justice Department's request.

"Our author knows that the President is determined to unmask whistleblowers who may be in his midst. That's one of the reasons A WARNING was written," Javelin said in a statement. "But we support the publisher in its resolve that the administration's effort to intimidate and expose the senior official who has seen misconduct at the highest levels will not prevent this book from moving forward."