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

The letter comes in the midst of President Donald Trump attacking Bolton on Twitter, and Bolton’s lawyer accusing the White House of corrupting the vetting process for Bolton’s book by sharing the contents of the book with those outside the National Security Council’s Records Management Division.