President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE has undertaken an effort to determine who cooperated with veteran journalist Bob Woodward for his forthcoming book about the White House, CNN reported Wednesday.

Two unidentified officials who have spoken with the president told the network that Trump is happy with initial denials from chief of staff John Kelly John Francis KellyMORE and Defense Secretary James Mattis James Norman MattisBiden courts veterans amid fallout from Trump military controversies Trump says he wanted to take out Syria's Assad but Mattis opposed it Gary Cohn: 'I haven't made up my mind' on vote for president in November MORE, but is looking to see who else pushes back against claims published in the book.

"He wants to know who talked to Woodward," one official told CNN.

An official told the network that it is unclear if anybody will lose their job because it would give credibility "to a book [Trump] is trying to discredit."

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CNN reported that Trump believes former national security adviser H.R. McMaster and former economic adviser Gary Cohn Gary David CohnGary Cohn: 'I haven't made up my mind' on vote for president in November Kushner says 'Alice in Wonderland' describes Trump presidency: Woodward book Former national economic council director: I agree with 50 percent of House Democrats' HEROES Act MORE may be responsible for anecdotes in the book, since they are featured prominently in excerpts.

The first excerpts from Woodward's book, "Fear: Trump in the White House," were published on Tuesday, and painted a portrait of a White House rife with in-fighting and undergoing a "nervous breakdown."

The excerpts included numerous quotes in which Trump and his top aides insult each other.

Trump, for example, mocked Attorney General Jeff Sessions Jefferson (Jeff) Beauregard SessionsGOP set to release controversial Biden report Trump's policies on refugees are as simple as ABCs Ocasio-Cortez, Velázquez call for convention to decide Puerto Rico status MORE’s accent when speaking with another staffer, according to the book, and described him as “mentally retarded” and “this dumb Southerner.”

Trump also reportedly told Commerce Secretary Wilbur Ross Wilbur Louis RossTrump admin asks Supreme Court to fast-track excluding people in U.S. illegally from census Trump 'very happy' to allow TikTok to operate in US if security concerns resolved TikTok, WeChat to be banned Sunday from US app stores MORE he didn’t trust him to negotiate, suggested former national security adviser H.R. McMaster dressed “like a beer salesman” and called former chief of staff Reince Priebus Reinhold (Reince) Richard PriebusLeaked audio shows Trump touted low Black voter turnout in 2016: report Meadows joins White House facing reelection challenges Trump names Mark Meadows as new chief of staff MORE “a little rat.”

Kelly is said to have called Trump an "idiot" and "unhinged" and described working in the White House as "Crazytown," while Mattis suggested Trump acts like a "fifth- or sixth-grader."

Trump and the White House have attacked Woodward's credibility in response to the book, which is due out on Sept. 11.

“This book is nothing more than fabricated stories, many by former disgruntled employees, told to make the president look bad,” White House press secretary Sarah Huckabee Sanders said in a statement.

Kelly denied he called Trump an idiot, reissuing a statement he provided after NBC News reported in April that he used the same term to describe Trump.

“I’m committed to the President, his agenda, and our country,” Kelly said Tuesday. “This is another pathetic attempt to smear people close to President Trump and distract from the administration’s many successes.”

Mattis issued a separate statement denying that he ever said or heard the statements attributed to him in the book excerpts.

“While I generally enjoy reading fiction, this is a uniquely Washington brand of literature, and his anonymous sources do not lend credibility,” Mattis said.

Woodward has stood by his reporting.

While Trump has suggested Woodward is a "Dem operative" and claimed he has "credibility problems," The Washington Post published audio and a transcript of a phone call between the president and the Watergate reporter last month.

In that conversation, Woodward explains that he contacted a half-dozen aides in an attempt to interview the president, while Trump said he never heard about the requests.

“It’s really too bad, because nobody told me about it, and I would’ve loved to have spoken to you,” Trump told Woodward. “You know I’m very open to you. I think you’ve always been fair.”