Washington — National security adviser Robert O'Brien told "Face the Nation" he is "very confident" no one within the National Security Council leaked the contents of a manuscript by his predecessor, John Bolton. Bolton's forthcoming book, according to reports in The New York Times, describes the president linking aid to Ukraine and investigations to the Bidens while urging Bolton to call Ukraine's president about the situation.

The Senate voted against hearing from Bolton and any other witnesses in the ongoing impeachment trial in a 49-51 vote Friday. Bolton's book is scheduled to be released March 17, but the National Security Council (NSC) told Bolton's attorney in a letter that the manuscript contains a wealth of classified information and cannot be released as-is. The book, entitled "The Room Where It Happened: A White House Memoir," was submitted to the NSC for review in late December, a standard procedure.

"I am very confident that the leaks of that book did not come from the NSC," O'Brien told "Face the Nation" moderator Margaret Brennan.

O'Brien did not directly answer whether he has reviewed the manuscript from his predecessor. Asked about any Bolton notes describing the alleged situations, O'Brien said, "I think that's something that's going to be investigated.

O'Brien emphasized the importance of keeping classified material classified, and said it's "always disappointing" when someone who has access to such information decides to write a "tell-all book."

Bolton has years of experience handling classified material, and some administration critics have suggested Bolton would have known what he could and could not have included in a memoir.

Bolton's reported revelations were considered bombshells but did not change the trajectory of the Senate trial, which is expected to conclude with a Wednesday vote on acquittal. The president is scheduled to deliver the State of the Union the night before.

On another topic, O'Brien said he believes the Chinese are being transparent about the spreading strain of coronavirus, which has now infected thousands of people in China. There are eight confirmed cases in the United States.

"This is a worldwide concern," said O'Brien. The U.S. declared the virus a public health emergency late last week.

Bolton's book publisher is Simon & Schuster, a subsidiary of ViacomCBS.