In a new afterword to Michael S. Schmidt’s Donald Trump v. the United States, the author reports that former President Donald Trump floated the idea of attacking North Korea with nuclear weapons, NBC News reports.

Schmidt makes the claim in the paperback edition of his book, originally published in 2020. In a starred review, a critic for Kirkus called it “a detailed, deeply reported portrait of a president willfully obstructing justice—with plenty of help.”

In the afterword, Schmidt writes that Trump suggested the idea to John F. Kelly, the president’s chief of staff from 2017 to 2019.

“What scared Kelly even more than [Trump’s] tweets [goading North Korea] was the fact that behind closed doors in the Oval Office, Trump continued to talk as if he wanted to go to war,” Schmidt writes. “He cavalierly discussed the idea of using a nuclear weapon against North Korea, saying that if he took such an action, the administration could blame someone else for it to absolve itself of responsibility.”

Kelly, according to the book, pushed back, telling Trump, “It’d be tough to not have the finger pointed at us.”

Trump had a complicated relationship with North Korea’s supreme leader, Kim Jong-un. The two met three times and were frequent correspondents, but also traded insults, with Kim once calling Trump a “dotard,” “gangster,” and “frightened dog.”

The paperback edition of Donald Trump v. the United States is slated for publication next Tuesday by Random House.

Michael Schaub, a journalist and regular contributor to NPR, lives near Austin, Texas.