Transcript for Comey says Trump asked him to investigate 'dossier'

Wee a big Friday re. First look at my excve interview with James Comey. Of course,was the director firedy president trump. That was an eventt shook washon, sparked the appointment of counsel Robert Mueller. The white house has attacked Comey calling him a liar B new ABC news poll out this morning suggests Americans, 48% to 32% findames Comey more believable than the president. And a lot of hinrom Comey's new book this morni including John kellyalling president trump firing Comey and the forme FBI director even comparing the pres to a mob boss, Ver strong words. He did that time andime again. He also writing thathe president is unethical, untethered to truth and he went even farther in the terview. I spent several hours this week hi it was such INT experience. I couldn't Bel at times W I was hearing andomeyid, he could not believe W he was saying. Startling and unprecedented judgments from a former director about a sittingpresident. January 6th,2017, trump tower. Directores Comey set to meet president-elect Donald Trump for the first time. As you headed into trump tower that Y, were you nervous? Yes. Reporter: Comey W group of intelligence ay heads briefing trump and his T aidesn how the Russians interfered in our election. President-elect trump's first question W to confirm that ha no impact on the election and the the conversation to rprise moved into a pr this and about drafting a P release with us still sitting there and the reason that so striking to me I that is just not done, that the intelligence community does intelligence the white house does pr and spin. You alsoaide strike by what they didn't as Very much.noo my recollection asked so what -- what's coming next from the Russ? How might we stop it? 'S the future look ? It was all, what can we say about whahe did and how it cts thelection that we Ju ha Reporter: Comey then asked meet alone with trump to warn about that now infamous steeossier unverified information on trump's T to Russia including aations O trump's encounters with prostitutes in . I'mbout to meet with a son who doesn't know just elected presid of the united States by all account androm my watching him dg the campaign could be volatile, and I'm about to talk to him about allegations that he wasolved with prostitutes in Moscow and that the Russians tap it and have leverage ove him. Was there any choice there? Why IFS was salacious and this pcular part of the Dossie unverified, sti unverified, by the way? So far -- when I got fit unvefied. Did you tell him the Steele dossier was financed by his political opponents. No ion't think I the term dossier. Did he have righto know that. Anced by his political opponents? I don't know tnswer to that. It wasn't necessary fory goal which was to alert him that W had this information. How graph didou get? I think a graphic as I needed to be. I started telling him about the allen was that he had been volved with prostitut a hotel in Moscow in3 during sit for the miss unie paant and that the Russians hadilmed episode and H interrupted veryefensively a started talking about I look like a guy who needs hrs and I -- since he was ask rhetorically I didn'nswer and moved on and explained, I not saying we credit this, I'm not saying we believe it. We just thought it very imt know. You tell him you thought it wasn't truer you didn't know if it true ornot. I never said I D believe it because I cn'tay one way or another. As that briefing? Really weird. It was almost an out-of-body rience forme. I was floating above myself looking down sayin you'r sitting here briefing the incong president of the united States aboutro in Moscow. January 27th, at a private dinner in the white use, ident trump raised the issueagain. He says he may me to investigate it to prove that I didn't happen and then he says, something that distracted me. He said there's even a 1% Chan my wife thinks that's that's terrible. And I remember thinking, how could you're think there's a 1% chance yere with prostitutes in Moscow. I'm a flawed human being but literall zero cha mife would think that's true. At kind of marriage to what kindf man does your wife think there's on a 99% chance you 'T do THA and I said to sir, when hetarted talking bit, I may order you T stigate that, I said, sir, 'S up to you but you'd want be careful about that because it might create a narrativehat 're investigating you personally and, second, I ry difficult to prove something dt happen. Did you believeis denial? Hony never thoug these word was could out of my moutut I don'tw whether the current president. Un states was with prostitutes in Moscow in 2013. It's possible but I don't know. I G to say that took my breath . I would imagine so. The presi C back to what he said again and again and He said that again and aga again. As you were sayingefore we went to that piece that he went further. Comey went further than W expecting, even more so than what H tal about in the book. When you pus hn his judgments about the president, when P him on his actions, he's both reflective,esn't giv some ground on some things Bute is just not holdin back O president trump in any way, shape O . He talks about how it was an out-of-by experience for him to sit with T president. T have for you. We were thereor several hours on mondaynd there W probably about 15 or0 of us in the room andollectively I prepared well for th I thought I knew the story, llectively we weren't ready for everything that he was getting Reado say. I've known you for a L time and you come back from interviews all the time and I do think I've ever seen you the reaction you had Ng back from this. It really did stun me.

This transcript has been automatically generated and may not be 100% accurate.