WATCH: CNN's Cuomo corners flailing Rudy Giuliani on White House lies in trainwreck interview

CNN's Chris Cuomo made Trump attorney Rudy Giuliani squirm when he asked him why the White House had lied about President Donald Trump's role in dictating a misleading statement about Donald Trump Jr.'s meeting with Russian agents.

After noting that a leaked letter written by Trump's legal team showed that they admitted that Trump had dictated the statement -- directly contradicting White House officials who insisted otherwise in 2017 -- Cuomo bluntly asked Giuliani, "Why did they choose to lie about his role in drafting this statement?"

Giuliani responded by laughing nervously and replied that Cuomo shouldn't accuse them of lying when, in reality, they had merely made "a mistake."

"That's a lot of mistakes," Cuomo said.

Giuliani stuck with this line, however, and insisted nothing nefarious had gone on even though the White House on Monday refused to explain its rationale for claiming that Trump had nothing to do with drafting the statement.

"It was a mistake!" the former New York mayor insisted. "I swear to God, it was a mistake. The guy made a mistake. He corrected it."

Cuomo then played clips of Trump attorney Jay Sekulow and White House Press Secretary Sarah Huckabee Sanders flat-out saying that Trump had nothing to do with the statement before turning back to Giuliani.

"Somebody is lying," Cuomo said. "It's not the kind of information that you would get wrong, that you wouldn't be privy to, that would change. Somebody is lying about this, Rudy, and I don't understand why."

Watch the video below.