Former Trump campaign adviser Sam Nunberg said Thursday that President Trump is "a stubborn, stubborn man," following a report detailing the tensions between advisers during Trump's transition into the White House.

"He is a stubborn, stubborn man. In a way where you can argue with him about what he needs to know, you can argue with him about what he wants to do, but I'll tell you what, he's sitting in the Oval Office," Nunberg told CNN's Erin Burnett.

"He's not going to change, that is him. That is it," he said.

In an excerpt from his upcoming book "Fire and Fury: Inside the Trump White House," author Michael Wolff described the former real-estate mogul, who describes himself as a shrewd negotiator, as being "volatile" and difficult to converse with.

Nunberg, a Republican policy analyst, is quoted in the book as saying he "got as far as the Fourth Amendment" in trying to explain the constitution to then-candidate Trump, "before his finger is pulling down on his lip and his eyes are rolling back in his head."

Trump also reportedly told Nunberg "I can be the most famous man in the world," regarding his goals for the campaign, which Wolff writes that he was not expecting to win.

"I'm surprised from reading the book; I don't know this because I don't talk to him while he's in the White House. I can see he's not going to change," Nunberg added. "That is him."