Donald Trump’s former national security adviser HR McMaster said on Monday that he would no longer work for the former president.

The retired lieutenant general, who worked in the Trump administration for 13 months from February 2017, appeared on Anderson Cooper 360 to promote his new book, At war with ourselves: My work in the White House under TrumpTrump’s spokesman has already dismissed the book as “nothing more than fake news” because of its outrageous claims. McMaster wrote that Russian President Vladimir Putin manipulated Trump by “using flattery to exploit his ego and insecurities.”

CNN host Anderson Cooper asked McMaster if he believed Trump’s former White House chief of staff, John Kelly, who had claimed that Trump had called wounded and killed American soldiers “suckers” and “losers” (Trump denies making those remarks).

McMaster said he felt the comments were “out of character” and that he had “never heard the president say anything like that, that bad,” but “of course” he had heard Trump criticizing his “dear friend,” the late Senator John McCain. Trump said in 2015 that McCain was a “war hero because he was captured” when his plane was shot down during the Vietnam War, adding, “I like people who weren’t captured.”

“The president is often very abusive, brash and says things that are completely out of line,” McMaster said. “I’ve recounted many of them in my book. But you know what, he’s an extremely disruptive person. I didn’t see it as my job to constrain him, but to help him disrupt what needed to be disrupted.”

Cooper then asked McMaster if he would work in a Trump White House again. “No,” McMaster replied immediately. “I would work in any administration where I feel like I can make a difference, but I’ve kind of had enough with Donald Trump.”

When asked whether he would work for Vice President Kamala Harris if she won the election in November, McMaster was less clear, but indicated that this was also unlikely.

“I don’t know if I could be effective there either, probably because of the different perspectives,” McMaster said.

McMaster’s interview also coincided with the third anniversary of the bombing of the Abbey Gate outside Kabul airport, which killed 13 American soldiers and more than 100 Afghan civilians during the chaotic withdrawal of US troops from Afghanistan.

During a visit to Virginia for a wreath-laying ceremony at Arlington National Cemetery on Monday, Trump said he would have “the resignations of every single senior official who had anything to do with the disaster in Afghanistan on my desk by noon on Inauguration Day,” adding: “You have to fire them, like on The Apprentice.”

Cooper asked McMaster how Trump himself had “handled” the issue, citing a passage in which McMaster wrote that Trump’s decisions “set the stage for the Biden administration’s humiliating withdrawal from Kabul in August 2021.”

“He couldn’t stick to his decision,” McMaster said, referring to Trump’s change of heart on his original decision in 2017 to maintain the U.S. presence in Afghanistan. “He didn’t stick to his decision. And I think people were constantly whispering mantras like ‘End the endless wars,’ ‘Afghanistan is a graveyard of empires,’ and so on, and manipulating him.”

Cooper asked McMaster if he believed Trump bore at least “some responsibility” for what happened during the withdrawal from Afghanistan – an episode Trump called on Monday “the most EMBARRASSING moment in the history of our country.”

“Oh yes,” McMaster replied.