Comey, who has been a vocal critic of Trump since being fired in May 2017, said he would be a “coward” for not speaking out and questioned the former defense secretary’s reluctance to denounce Trump or his policies.

After calling himself “an admirer of Jim Mattis as a leader” during a book conversation in New York City on Wednesday, Comey said, “I don’t get his explanation for why he isn’t speaking about what he knows.”

“He doesn’t have to share confidential, classified conversations with the president,” Comey continued. “But you are a civilian leader who has a perspective that would be useful to the American people. What’s the reason you’re not sharing that?”