WASHINGTON - Prosecutors on Thursday unveiled threatening text messages by U.S. President Donald Trump's adviser Roger Stone to radio host Randy Credico in which Stone urged Credico not to testify about their communications over Stone's efforts in 2016 to learn when WikiLeaks might release more damaging emails about Trump's rival Hillary Clinton."Prepare to die ..." Stone wrote in one profanity-laced text to Credico. "You are a rat."In text messages, shown as exhibits during Stone's criminal trial in federal court in Washington, Credico confronted Stone about his September 2017 testimony to the House of Representatives Intelligence Committee.Stone testified he had a back channel to WikiLeaks website founder Julian Assange, who alerted him in the summer of 2016 that more damning emails about Clinton would be released.Stone identified Credico, who had interviewed Assange on his radio show, as the secret source of his intelligence in a subsequent letter to the committee.But when the committee and Special Counsel Robert Mueller later sought to corroborate Stone's claim by asking Credico to testify, Credico realized Stone had lied about him being a back channel and fudged the timeline to make it sound like Credico had provided information in July, when in fact Credico did not actually interview Assange until a month later."I don't know why you had to lie and say you had a backchannel," Credico later told Stone in texts sent in early December 2017. "You could have just told them the truth ... You want me to cover you for perjury now.""I guarantee you, you are the one who gets indicted for perjury if you are stupid enough to testify," Stone replied.Stone, a self-described "dirty trickster" and "agent provocateur," has pleaded not guilty to charges of obstructing justice, witness tampering and lying to the House intelligence committee in its investigation into Russia interference in the 2016 election.Stone in various texts urged Credico to plead the Fifth Amendment against self-incrimination or not talk to investigators. He made references to "Frank Pentangeli" - a character in the film "The Godfather Part II" who recants his testimony to Congress about a mobster amid witness intimidation.Stone also sent other threatening texts and seemed to suggest he would harm Credico's small white dog, Bianca.Credico ultimately did plead the Fifth before the committee, but later agreed to be interviewed by the FBI.Of the seven counts Stone faces, witness tampering carries the highest potential prison sentence - a maximum of 20 years. Obstruction and lying to Congress carry a maximum of five years each.Stone's lawyer Bruce Rogow told the jury in opening statements on Wednesday that his client did not willfully and intentionally mislead Congress, and said Stone did not have any intermediaries with Wikileaks.