President Trump Donald John TrumpBiden leads Trump by 36 points nationally among Latinos: poll Trump dismisses climate change role in fires, says Newsom needs to manage forest better Jimmy Kimmel hits Trump for rallies while hosting Emmy Awards MORE's personal attorney Rudy Giuliani Rudy GiulianiDemocrats fear Russia interference could spoil bid to retake Senate Grand jury adds additional counts against Giuliani associates Lev Parnas and and Igor Fruman Juan Williams: Breaking down the debates MORE denounced former national security adviser John Bolton John BoltonDiplomacy with China is good for America The Hill's Morning Report - Sponsored by The Air Line Pilots Association - Pence lauds Harris as 'experienced debater'; Trump, Biden diverge over debate prep DOJ launches probe into Bolton book for possible classified information disclosures MORE as a "backstabber" in an interview set to broadcast Wednesday.

Giuliani tore into Bolton in the interview with "CBS This Morning" in the wake of reports that Bolton was critical of him and raised concerns about his activities in Ukraine to other administration officials.

"He never said to me, 'I've got a problem with what you are doing in Ukraine,'" Giuliani said. "Never once, never winked, never sent me a little note. He is a personal friend, I thought. So here's the only conclusion I can come to, and it's a harsh one, and I feel very bad about it: He's a backstabber."

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"If your friend was complaining about you behind your back and didn't have the guts to come up to your face and tell you, 'I think you're screwing up' ... that'd be a backstabber," he continued. "That's classic backstabber. So I feel I got a swamp character here."

The New York Times reported Sunday that Bolton wrote in a draft of his forthcoming memoir that Trump said in an August meeting that he did not want to release security aid for Ukraine until the country agreed to investigate his political rivals, a claim that cuts to the heart of the impeachment efforts against Trump.

Bolton also reportedly wrote that he raised concerns to Attorney General William Barr Bill BarrSunday shows - Ruth Bader Ginsburg's death dominates What Attorney General Barr really said about justice Pelosi: House will use 'every arrow in our quiver' to stop Trump Supreme Court nominee MORE and Secretary of State Mike Pompeo Michael (Mike) Richard PompeoUS reimposes UN sanctions on Iran amid increasing tensions Sunday shows preview: Justice Ginsburg dies, sparking partisan battle over vacancy before election Trump steps up Iran fight in final election stretch MORE about Giuliani's involvement in Ukraine matters, suggesting to Pompeo that Giuliani may have wanted former U.S. Ambassador to Ukraine Marie Yovanovitch Marie YovanovitchGrand jury adds additional counts against Giuliani associates Lev Parnas and and Igor Fruman Strzok: Trump behaving like an authoritarian Powell backs Biden at convention as Democrats rip Trump on security MORE removed from her post because she was targeting his private clients as part of an anti-corruption agenda.

Bolton left the White House last September amid tensions with Trump and other staffers.

The reported claims have amplified Democrats' efforts to include witnesses such as Bolton in Trump's ongoing impeachment trial, which GOP leadership has resisted so far.

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Giuliani has been a central character in the impeachment saga. Multiple current and former administration officials testified last year that the former New York City mayor was conducting a shadow foreign policy in Ukraine to dig up dirt on Democrats and that he led an effort to oust Yovanovitch.

Giuliani and a host of other Trump allies have made a concerted effort to question Bolton's credibility and accuse him of trying to juice book sales with his allegations, which were reported in the middle of Trump's impeachment trial.

Trump has denied he told Bolton security aid for Ukraine was tied to investigations, White House press secretary Stephanie Grisham Stephanie GrishamIvana Trump on Melania as first lady: 'She's very quiet, and she really doesn't go to too many places' The Hill's 12:30 Report: Trump uses White House as campaign backdrop Coronavirus tests not required for all Melania Trump speech attendees: report MORE has accused Bolton of selling out national security and a number of Fox News hosts with whom Bolton used to work have decried him as disloyal.