DURHAM, N.C. — John R. Bolton, the former national security adviser to President Trump, suggested on Monday that his unpublished book contained far more revelations than just the campaign to pressure Ukraine for help with domestic politics but said he was fighting “censorship” by the White House.

In his first public appearance since the Senate impeachment trial in which Republicans refused to hear his testimony, Mr. Bolton said that the White House was trying to keep him from publishing important parts of his new memoir by terming them classified. He said he was pushing back but feared that a pre-publication review could stop the book from being published next month.

“For all the focus on Ukraine and the impeachment trial and all that, to me, there are portions of the manuscript that deal with Ukraine, I view that like the sprinkles on the ice cream sundae in terms of what’s in the book,” Mr. Bolton told an audience at Duke University during a forum on foreign policy on Monday evening. “This is an effort to write history and I did it the best I can. We’ll have to see what comes out of the censorship.”

“I’m hoping ultimately I can get the book published,” Mr. Bolton said at another point. “I hope it’s not suppressed.” Reminded that the president had assailed him on Twitter, Mr. Bolton said: “He tweets, but I can’t talk about it. How fair is that?”