Washington (CNN) The White House has issued a formal threat to former national security adviser John Bolton to keep him from publishing his book, "The Room Where It Happened: A White House Memoir," sources familiar with the matter tell CNN.

The letter, which is dated January 23, said some of the information was classified at the "top secret" level, meaning it "reasonably could be expected to cause exceptionally grave harm to the national security."

"The manuscript may not be published or otherwise disclosed without the deletion of this classified information," the letter read.

The White House had no comment. Neither Bolton nor a spokesman for the publisher, Simon & Schuster, responded to a request for comment.

Read More