Transcript for New report claims Trump directed Cohen to lie

We move to the breaking news. A new report in buzzfeed claiming president trump directed his former fixer, Michael Cohen, to lie to congress about negotiations for a trump tower in Moscow. Report adds special counsel Robert Mueller has evidence to back that up. Congressional Democrats calling for an immediate investigation declaring that trump must be impeached if the story is true. Our chief justice correspondent Pierre Thomas has the latest. Reporter: Some Democrats on capitol hill are jumping on this report and calling for an immediate congressional investigation and some potential presidential candidates are now using the "I" word, impeachment. This morning, an explosive new report from buzzfeed news claiming president trump directed his former attorney, Michael Cohen to lie to congress about negotiations with Russia to build a trump tower in Moscow. Citing two law enforcement officials involved in an investigation of the matter, the article claims after the election the president instructed Cohen to say negotiations over the building project ended months earlier than it actually did. In an attempt to, quote, obscure trump's involvement. ABC news has not corroborated buzzfeed's account and overnight the president's current lawyer, Rudy Giuliani, told several media outlets if you believe Cohen, I can get you a great deal on the Brooklyn bridge. The buzzfeed report also claims special counsel Robert Mueller learned about the president's alleged directive to lie not just from Cohen but from interviews with witnesses from the trump organization, internal company emails and text messages. During the campaign president trump claimed he had no business ties with Russia. I don't deal there. I have no businesses -- I have no loans from Russia. Reporter: Late last year he likely looked at doing a building in Moscow. Cohen made clear to George Stephanopoulos that his actions were directed by president trump himself. He's saying very clearly that he never directed you to do anything wrong. Is that true? I don't think there's anybody that believes that. First of all, nothing at the trump organization was ever done unless it was run through Mr. Trump. Reporter: The issue of obstruction specifically addressed during William Barr's confirmation hearing for attorney general. In your memo you talked about the Comey decision and you talk about obstruction of justice and already went over that which I appreciate. You wrote on page one a president persuading a person to commit perjury would be obstruction, is that right? Yes. Reporter: Now responding to the new buzzfeed report the chairman of the house intelligence committee, Democrat Adam Schiff, called the allegations among the most serious to date vowing to do what's necessary to find out if it's true. We have no comment from Cohen so far and his attorneys last night did not comment on what could be a major development, a significant part of any Mueller report. Let's bring in Dan abramsegin with the basics. If the heart ofhetory is true, that in phone call or face-to-face meeting president trump says to Michael Cohen, go E to congress. Yeah, now it's easy, right? Up to this point we talked about where is the Lin for me people say to fire skitness tampering? This is easy. If he told Michael Cohen to lie to congress, no one would suggest that's not obstruction of justice or witness tampering and that would be a crime. It was the first impeachment order against Richard Nixon. We know what from Mueller said during Cohen's sentencing he provided useful information and described the circumstances preparing this false testimony to congress. What about it was more subtle than the president saying go lie. What if all the lawyers are sharing information and sharing stories they know are not true and saying we all have to be consistent, basically knowing that Michael Cohen is going to lie but not directing it. First of all I'll hope all the lawyers together gathering and sort of talking together about how to lie. They did have a joint defense. They did, they did, but a joint defense agreement is different than saying all the lawyers are getting together and saying we have to work on how to deal with this lie. So, but assuming it's a little grayer, assuming that it's unclear and that maybe there's an understanding and that there's no directive, that makes it a lot harder to prove because you need -- that's one of the most important points from this article is this idea that there are emails to back it up, that there were interviews with numerous witnesses, so you want to as much as possible investigating this take it out of Michael Cohen's hands and put it into the hands of others. Then finally in the article it does describe activity all during the campaign. Ten meetings with the president over the trump tower Moscow suggesting it's going to bring in $300 million. He needs Russian help for it. He's lying about it at a time that Russia is helping his campaign. And that no question will be part of the essence of Mueller's investigation. Because this is the most important point, when the Russians are hacking, the question is was anyone from the trump campaign in any way assisting in that meaning you don't have to actually be assisting in the hacking itself, could be the coordination, it could be the distribution, whatever the case may be but if they're coordinating, colluding is the word that everyone is talking about with the Russians, in some way, shape or form at that time, that is potentially perilous. Dan Abrams, thanks very much.

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