Transcript for Roger Stone says he won't rule out cooperation

Thank you, Tom. The Russia investigation. New developments considering Roger stone. The president's long time friend and adviser speaking out in a new interview with George. The big question, will he cooperate with the special counsel? Our chief justice correspondent Pierre Thomas is in Washington with more. Reporter: Stone is expected here in Washington in the next 24 hours for a court appearance on Tuesday. As we saw yesterday in his interview with George on "This week" the self-proe claimed dirty strik Cher is pushing back hard. Facing up to 20 years in prison if con viblgted, Roger stone vowing to fight the indictment. There is nothing to fight. It is designed to intimidate me or perhaps seek personal information that could be used to embarrass me. Reporter: Stone says it's all overkill. And is offended betty FBI's raid of his home on Friday. This was an expensive show of force to try to depict me as publ enemy number one. These are gestapo tactics. Reporter: He didn't rule out cooperating with prosecutors. Any chance you'll cooperate? That is a question I would have to determine after my attorneys have some discussion. If there's wrongdoing by other people in the campaign, that I know about, which I know of none, but if there is, I would certainly testify honestly. He's never suggested to you in any way, shape, or form, that he might offer you a pardon? Absolutely, positively not. Reporter: Stone is accused of serving as an intermediary with the trump campaign and wikileaks, which publishes those damageses e-mails about the Clinton campaign. E-mails said to be hacked from the DNC and Clinton's campaign chair, John podesta. In context with senior trump campaign official when he learned the FBI and congress began investigating Russian interference. He's accused of lying to congress, obstruction, and witness tacherring. He might cooperate with the special counsel. But he says he'll never bear false witness against president trump. Thank you, Pierre. Let's bring Chris Chris tee

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