Former FBI Deputy Director Andrew McCabe appeared surprised by the claim that White House officials put together a tally of Cabinet officials they believed would support using the 25th Amendment to remove President Trump from office.

The upcoming book The Warning, written by the anonymous Trump administration official who authored a "resistance" op-ed last year, says high-level White House officials put together a "back-of-the-envelope" tally on what officials they thought would be willing to sign a letter to invoke Section 4 of the 25th Amendment declaring the president unfit to perform his duties after he fired FBI Director James Comey.

According to contemporaneous notes written by McCabe, who assumed the role of acting FBI director in May 2017 following Comey's ouster, a very frazzled Deputy Attorney General Rod Rosenstein discussed with him the prospect of using the 25th Amendment. Rosenstein quickly released a statement that said "there is no basis to invoke the 25th Amendment" based on his experiences with Trump. He is also said to have tossed around the idea of wearing a wire to record conversations with Trump.

McCabe was fired from the FBI on the eve of his retirement and is now a contributor on CNN, where on Thursday he said he didn't have any prior knowledge of a list of Cabinet officials who may have supported using the 25th Amendment.

"That’s why this kind of revelation is particularly interesting to me, because I assumed that the discussion that Mr. Rosenstein and I had was simply Rod kind of gaming things out in his head. I never thought that he’d — he never indicated to me ... that he talked about it with anyone else or that the people he was thinking about, that he’d had any conversations with them," McCabe said.

"This is really like — he thought this person and that person might go along with it, but he never indicated he’d actually discussed it with them," he added.

According to excerpts from the The Warning obtained by the Huffington Post, the high-level White House officials who put together the tally believed Vice President Mike Pence would be in favor of using the 25th Amendment if a majority of the Cabinet agreed to it, but nothing ever materialized from those discussions. The report does not indicate these White House officials had any contact with McCabe.

Pence and his office have denied he was privy to any discussions about such an effort to remove Trump and grant Pence the role of acting president. During an appearance in New Hampshire on Thursday, Pence also called on the anonymous Trump administration official to "do the honorable thing and resign" due to his or her lack of support for the president.

McCabe praised the anonymous official for writing about the White House discussions on invoking the 25th Amendment.

"I know I and my staff were in a great quandary trying to figure out exactly why he had done that and what this meant not just for our investigation but for the FBI in general and the country in general and I think that these sorts of conversations are helpful and they show just the kind of almost panic that people in and around the administration were in as a direct result of the president’s decision to fire the director," he said.

McCabe, who has been critical of Trump and wrote a book about the president's clash with the FBI, also said he would not write such a book anonymously.

"The way that I would approach this situation, were I that person — I think it’s admirable that when people want to bring their concerns to the forefront and share what they understand with the American people, that put people in a position to make a better decision, but I think it’s better to do that, clearly indicating who you are. It gives the reader and public an ability to assess what you’re asserting and to assess, like, how could you possibly know the things that you’re including in your statement or your book?" he said. "So, I think it’s really challenging to do something like this anonymously. It raises all kinds of other issues that get in the way of the message."