Author Bob Woodward disputed denials from White House chief of staff Gen. John Kelly and Defense Secretary Gen. Jim Mattis about his book’s reporting surrounding their disparaging comments about President Donald Trump.

“They are not telling the truth,” Woodward said in an interview with NBC anchor Savannah Guthrie. “These are political statements to protect their jobs, totally understandable.”

Woodward resisted Guthrie’s attempts to verify his sourcing for his book about Trump, warning Americans that the president was putting the country in grave danger.

When Guthrie asked Woodward if he had a source for the book that later lied about the information they have him, he resisted.

“You want to use the ‘lie’ word, what I want to do is focus on … here’s the problem, this has not been treated seriously enough … and some of the things that Trump did (and does) jeopardized the real national security,” he said.

Woodward said that Trump was endangering secret military “special access” programs and said that his views on tariffs were also damaging to the country.

“The experts, 99.9 percent of people say, ‘Don’t do tariffs it doesn’t work,’ he’s got it in his head, and when people challenge him he’ll say, ‘Oh I’ve had those ideas for 30 years, you’re wrong,'” Woodward said.

Trump reacted to the interview on Twitter, calling Woodward a “liar.”