'You called me a liar,' Warren told Sanders post-Iowa debate

Elizabeth Warren accused Bernie Sanders of calling her a liar before a national television audience during a tense, post-debate exchange in which she refused to shake his outstretched hand, according to  audio released Wednesday by CNN.

The Democratic presidential rivals are strong progressives who had steadfastly refused to attack each other for more than a year on the campaign trail. But that changed Monday, when Warren said that, during a private meeting between the two in 2018,

Sanders, a senator from Vermont, has denied that, and did so again during Tuesday night's

That exchange lasted only a few minutes. But after the debate was over, Warren, a Massachusetts senator, approached Sanders, who put out his hand for her to shake. Instead, she confronted him, and the two talked briefly in tense tones.

Neither campaign would confirm what was said Tuesday night, but CNN released the audio Wednesday. As she is refusing his extended hand, Warren repeats, “I think you called me a liar on national television." Sanders gently brushes her with his hand, then says, “Let's not do it right now.”

“You want to have that discussion?” he continues. “We'll have that discussion." Warren replies, “Anytime.”

Sanders then adds, “You called me a liar,” before concluding, “All right, let's not do it now.”

The exchange was interrupted by fellow candidate and environmentalist Tom Steyer, who said, “I don't want to get in the middle of it” and greeted Sanders as the senator walked away.

Warren's and Sanders' aides have for days attempted to de-escalate the feud

Release of the audio is likely to ensure the political fight continues — at least for now.