Former White House national security adviser John Bolton on Monday questioned whether it was “fair” that President Donald Trump has called him a liar on the subject of Ukraine, but “I can’t talk about it.”

In his first public remarks since Trump was impeached by the House and acquitted by the Senate, Bolton said his own views of national security policies, and descriptions of interactions with Trump on Ukraine and other issues, risk being “suppressed” and censored by the administration.

His ability to speak was restrained, he said, because of the White House “prepublication review” of his forthcoming book “and threats of possible legal action.”

In a 90-minute question-and-answer session before students, faculty and members of the public at Duke University, Bolton voiced familiar hard-line views on North Korea, Iran and other issues. He said he viewed Ukraine and the impeachment “as sprinkles on the ice cream sundae” compared with other subjects he deals with in the book.

Asked whether he agreed with the president’s assessment that Trump’s July call with Ukrainian President Volodymyr Zelensky was “perfect,” Bolton said “You’ll love Chapter 14.”

Palestinian protests against President Trump's Middle East peace plan Show all 18 1 /18 Palestinian protests against President Trump's Middle East peace plan Palestinian protests against President Trump's Middle East peace plan TOPSHOT - Palestinian demonstrators chant slogans and wave Palestinian flags as they stand by flaming tyres during a protest against US President Donald Trump's expected peace plan proposal in Gaza City on January 28, 2020. (Photo by MAHMUD HAMS / AFP) (Photo by MAHMUD HAMS/AFP via Getty Images) MAHMUD HAMS AFP via Getty Palestinian protests against President Trump's Middle East peace plan Palestinian protesters burn pictures of US President Donald Trump and Israel's Prime Minister Benjamin Netanyahu during a demonstration in the West Bank against the expected peace plan proposal AFP via Getty Palestinian protests against President Trump's Middle East peace plan US President and Israeli Prime Minister Benjamin Netanyahu announce Trump's Middle East peace plan in the White House AFP via Getty Palestinian protests against President Trump's Middle East peace plan Palestinians protest as smoke rises from burning tires ahead of the announcement by U.S. President Donald Trump of his long-delayed Mideast peace plan, in Gaza City January 28, 2020. REUTERS/Mohammed Salem TPX IMAGES OF THE DAY MOHAMMED SALEM Reuters Palestinian protests against President Trump's Middle East peace plan Palestinian demonstrators chant slogans as they stand by flaming tyres during a protest against US President Donald Trump's expected peace plan proposal in Rafah in the southern Gaza Strip . - Palestinians staged protests against US President Donald Trump's Middle East peace plan, hours before it was to be unveiled in Washington. Thousands demonstrated in Gaza, burning pictures of Trump and the American flag, while further rallies were planned for the coming days. (Photo by SAID KHATIB / AFP) (Photo by SAID KHATIB/AFP via Getty Images) SAID KHATIB AFP via Getty Palestinian protests against President Trump's Middle East peace plan Palestinian protesters wave the national flag during a demonstration in the West Bank city of Ramallah on January 28, 2020, against US President Donald Trump's expected peace plan proposal. - Palestinians staged protests against US President Donald Trump's Middle East peace plan, hours before it was to be unveiled in Washington. Thousands demonstrated in Gaza, burning pictures of Trump and the American flag, while further rallies were planned for the coming days. (Photo by Ahmad GHARABLI / AFP) (Photo by AHMAD GHARABLI/AFP via Getty Images) AHMAD GHARABLI AFP via Getty Palestinian protests against President Trump's Middle East peace plan U.S. President Donald Trump gives a thumbs up while listening to Israel's Prime Minister Benjamin Netanyahu address a joint news conference to discuss a new Middle East peace plan proposal in the East Room of the White House in Washington, U.S., January 28, 2020. REUTERS/Brendan McDermid BRENDAN MCDERMID Reuters Palestinian protests against President Trump's Middle East peace plan epa08172847 Palestinians chant slogans during a protest against the so-called 'Deal of the Century', planned by Trump to solve the conflict between Palestinians and Israel, in the streets of Gaza City, Gaza Strip, 28 January 2020. EPA/MOHAMMED SABER MOHAMMED SABER EPA Palestinian protests against President Trump's Middle East peace plan epa08172814 A Palestinian holds a banner reading in Arabic 'down with the deal of century' as people protest against the deal planned by Trump to solve the conflict between Palestinians and Israel, in the streets of Gaza City, Gaza Strip, 28 January 2020. EPA/MOHAMMED SABER MOHAMMED SABER EPA Palestinian protests against President Trump's Middle East peace plan Palestinian protesters burn pictures of US President Donald Trump during a demonstration in the West Bank city of Ramallah on January 28, 2020, against the expected peace plan proposal. - Palestinians staged protests against US President Donald Trump's Middle East peace plan, hours before it was to be unveiled in Washington. Thousands demonstrated in Gaza, burning pictures of Trump and the American flag, while further rallies were planned for the coming days. (Photo by Ahmad GHARABLI / AFP) (Photo by AHMAD GHARABLI/AFP via Getty Images) AHMAD GHARABLI AFP via Getty Palestinian protests against President Trump's Middle East peace plan Palestinian protesters wave the national flag during a demonstration in the West Bank city of Ramallah on January 28, 2020, against US President Donald Trump's expected peace plan proposal. - Palestinians staged protests against US President Donald Trump's Middle East peace plan, hours before it was to be unveiled in Washington. Thousands demonstrated in Gaza, burning pictures of Trump and the American flag, while further rallies were planned for the coming days. (Photo by Ahmad GHARABLI / AFP) (Photo by AHMAD GHARABLI/AFP via Getty Images) AHMAD GHARABLI AFP via Getty Palestinian protests against President Trump's Middle East peace plan epa08172866 Palestinians set fire during a protest against the so-called 'Deal of the Century', planned by Trump to solve the conflict between Palestinians and Israel, in the streets of Gaza City, Gaza Strip, 28 January 2020. EPA/MOHAMMED SABER MOHAMMED SABER EPA Palestinian protests against President Trump's Middle East peace plan epa08172871 Palestinians chant slogans during a protest against the so-called 'Deal of the Century', planned by Trump to solve the conflict between Palestinians and Israel, in the streets of Gaza City, Gaza Strip, 28 January 2020. EPA/MOHAMMED SABER MOHAMMED SABER EPA Palestinian protests against President Trump's Middle East peace plan epa08172842 Palestinians protesters burn a poster depicting US President Donald Trump during a protest against the so-called 'Deal of the Century', planned by Trump to solve the conflict between Palestinians and Israel, in the streets of Gaza City, Gaza Strip, 28 January 2020. EPA/MOHAMMED SABER MOHAMMED SABER EPA Palestinian protests against President Trump's Middle East peace plan Palestinian demonstrators chant slogans as they stand by flaming tyres during a protest against US President Donald Trump's expected peace plan proposal in Rafah in the southern Gaza Strip . - Palestinians staged protests against US President Donald Trump's Middle East peace plan, hours before it was to be unveiled in Washington. Thousands demonstrated in Gaza, burning pictures of Trump and the American flag, while further rallies were planned for the coming days. (Photo by SAID KHATIB / AFP) (Photo by SAID KHATIB/AFP via Getty Images) SAID KHATIB AFP via Getty Palestinian protests against President Trump's Middle East peace plan Palestinian protesters wave the national flag and a portrait of president Mahmud Abbas during a demonstration in the West Bank city of Ramallah on January 28, 2020, against US President Donald Trump's expected peace plan proposal. - Palestinians staged protests against US President Donald Trump's Middle East peace plan, hours before it was to be unveiled in Washington. Thousands demonstrated in Gaza, burning pictures of Trump and the American flag, while further rallies were planned for the coming days. (Photo by Ahmad GHARABLI / AFP) (Photo by AHMAD GHARABLI/AFP via Getty Images) AHMAD GHARABLI AFP via Getty Palestinian protests against President Trump's Middle East peace plan Palestinians chant slogans as they demonstrate outside the local government headquarters in Tulkarmm, west of Nablus in the occupied West Bank, on January 28, 2020 against US President Donald Trump's expected peace plan proposal. (Photo by Jaafar ASHTIYEH / AFP) (Photo by JAAFAR ASHTIYEH/AFP via Getty Images) JAAFAR ASHTIYEH AFP via Getty Palestinian protests against President Trump's Middle East peace plan Palestinian protesters chant angry slogans during a protest against the U.S. Mideast peace plan, in Gaza City, Monday, Jan. 28, 2020. U.S. President Donald Trump is set to unveil his administration's much-anticipated Mideast peace plan in the latest U.S. venture to resolve the Israeli-Palestinian conflict. (AP Photo/Khalil Hamra) Khalil Hamra AP

Bolton left the administration in September, after 17 months as Trump’s third national security adviser, following policy rifts with the president. Trump announced via Twitter that he had fired Bolton, though Bolton, also via Twitter, said he had resigned. Bolton’s book about his time at the White House, titled “The Room Where It Happened,” is scheduled to be published March 17.

Portions of the book were leaked to The New York Times, including Bolton’s firsthand account of what he said were discussions with Trump about the president’s withholding of aid to Ukraine unless its government investigated his Democratic political rivals. Those allegations became the basis of Trump’s impeachment in December.

After the impeachment, Bolton offered to testify at the subsequent Senate trial, if subpoenaed, but the Republican majority voted not to call witnesses. The Senate this month acquitted the president on charges of abuse of power and obstruction. In recent weeks, the White House – to which Bolton submitted his book for national security vetting – has told him it has “serious concerns” about what it says is classified information in the book.

Bolton’s lawyer has disputed that assessment and asked for the White House to expedite completion of its review. It remains unclear whether publication will go ahead without White House approval.

“I hope it’s not suppressed,” Bolton said. “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 say things in the manuscript about what he said to me,” he said. “I hope they become public someday. He tweets, but I can’t talk about it. How fair is that?”

Bolton hinted that the book contains revelations on a number of subjects, but he declined to answer a number of specific questions. Asked for his account of Trump’s controversial meeting with Russian President Vladimir Putin in the summer of 2018, he said, “I could read a chapter from my book and give you an answer.”

“In my view, to pursue the right policies for America, I was willing to put up with a lot,” he said.

Bolton has denied leaking any of the manuscript and suggested that the revelations came from within the administration. “Probably with leaks coming out of the administration, in due course you’ll know everything that’s in the book.”

He voiced his well-known views about North Korea, saying the administration’s effort to persuade Pyongyang to abandon its nuclear weapons program was “going to fail.”

Despite Trump’s claims that North Korean leader Kim Jong Un has said he would do so, Bolton said there was “not a single piece of evidence that the government of North Korea intends to give up nuclear weapons.”

“This idea that they can be coaxed into giving up . . . their nuclear program was flawed from the start,” he said.

Pyongyang, he said, was “jiving the Americans” and is getting closer every day to the capability of dropping a nuclear weapon on American cities.

On Venezuela, Bolton said the administration’s “theatrics” were “not equivalent to support” for the removal of the government of President Nicolás Maduro.

Bolton said China, which he described as “the number one national security issue for the rest of the century,” may have known about the coronavirus epidemic “weeks and weeks before it was announced.”

About 1,000 people attended the free event. Outside, a protest drew about two dozen students and faculty members who objected to Bolton’s hard-line views.

After Bolton’s appearance was announced earlier this month, all available tickets were distributed within minutes.

Duke University has its own connection to prior impeachments. Richard M. Nixon, Class of 1937, and former Whitewater independent counsel Kenneth Starr, Class of 1973, earned their law degrees there.

Bolton is also scheduled to speak Wednesday, alongside former Obama administration national security adviser Susan Rice, at Vanderbilt University in Tennessee.