Transcript for Former Trump national security adviser Bolton: ‘I don’t think he’s fit for office’
Reporter: He was Donald Trump's longest-serving national security adviser, John Bolton, at president trump's side for some of our country's most important national security decisions. And what Bolton saw left him deeply disturbed. A president who puts reelection above the country's interest and makes decisions for personal gain, leading Bolton to a stunning conclusion. You describe the president as erratic, foolish. Behaved irrationally, bizarrely. You can't leave him alone for a moment, saw conspiracies behind rocks and was stunningly uninformed. He couldn't tell the difference between his personal interests and the country's interests. ? There really isn't any guiding principle it that I was able to discern other than what's good for Donald Trump's reelection. You say that you were astonished by what you saw. A president for whom getting reelected was the only thing that mattered, even if it meant endangering or weakening the nation? I think he was so focussed on the reelection that longer-testimony considerations fell by the wayside. So, if he thought he could get a photo opportunity with Kim Jong un at the demilitarized zone in Korea, there was considerable emphasis on the photo opportunity and little to what it meant for the bargaining positions for the United States. Reporter: Bolton, in his new book saying trump viewed the negotiations with the nuclear-armed North Korea as theater, asking how many people would be covering the event, and eager to present Kim Jong un with a trump-autographed copy of Elton John's "Rocket man" CD, the nickname trump had given Kim. Bolton saying giving this CD to Kim remain add high priority for several months. Not the only foreign leader he was trying to make deals. He asked China's president XI to buy U.S. Soybeans to help trump with farm states, pleading with XI to ensure he'd win. And Russia's president, Bolton said Vladimir Putin couldn't wait to get in a room alone with Donald Trump. How would you describe trump's relationship with Vladimir Putin? I think Putin thinks he can play him like a fiddle. I think Putin is smart, tough, he plays a bad hand extremely well. I think he sees that he's not faced with the serious adversary here, and he works on him, and I works on him and he works on I don't think he's worried about Donald Trump. The president may be a superb dealer with real estate in Manhattan, dealing with arms and many, many other security issues are things far removed from his life experience. When you're dealing with somebody like Putin, who has made his life understanding Russia's strategic position in the world, against Donald Trump, who doesn't enjoy reading about these issues or learning about them, it's a very difficult position for America to be in. Reporter: But Bolton has been heavily criticized himself, for not testifying in the impeachment hearing last year, saying now it was because the focus was too narrow and politicized and that congress should have investigated trump for additional possible impeachable offenses saying now he heard first hand from trump that security aid to Ukraine was directly tied to his request that Joe Biden and others be investigated by the Ukrainian president. Martha, good evening. You sat down with John Bolton for this highly-anticipated no-holds-barred interview, and the administration is still trying to stop the release of the book. What are the chances that that will succeed? John Bolton doesn't think it will succeed and it would be very, very difficult to stop this book from being released. Obviously, it's out there, there are hundreds of thousands of copies already in boxes ready to ship. There have been stories about, obviously the book day after day after day. So some of the information is I think it would be very, I have tough to stop this. And today, in a tweet, the president's calling John Bolton a whacko and that his book is made up of lies and false stories. We use the word unprecedented to describe this white house, yet this is one of the highest-ranking officials to ever speak out so negatively against a sitting president. What do you make of these war of words? I think unprecedented is the perfect word in this circumstance. He is the highest-ranking official I think in memory, in history to ever do this and talk so, so comprehensively. I know there's a lot of turnover in the trump white house. But for 17 months, John Bolton was at president trump's side for some of the most important foreign policy, and national security issues around. Martha, how would you describe his demeanor throughout? I think John Bolton was confident and calm. He seems to have quite the memory for every word in that book, no matter what I asked him. He could recall something from the book or something that happened to him. I think this is a man who took copious notes Fascinating. We look forward to it. You can watch the full interview, Sunday evening, 9:00/8:00 central right here on ABC.
This transcript has been automatically generated and may not be 100% accurate.