Former Green Party candidate Jill Stein pushed back against Hillary Clinton after the failed 2016 presidential candidate called her a "Russian asset" this week.

In a new interview, Clinton appeared to float a conspiracy theory that the Russians are “grooming” Hawaii congresswoman and Democratic presidential candidate Tulsi Gabbard to be a third-party candidate in 2020.

“I'm not making any predictions, but I think they've got their eye on somebody who is currently in the Democratic primary and are grooming her to be the third-party candidate,” Clinton said, an apparent reference to Gabbard. “She's the favorite of the Russians. They have a bunch of sites and bots and other ways of supporting her so far.”

She then accused Stein, who ran against her and Donald Trump in 2016, of also being an asset of Russia: "That’s assuming Jill Stein will give it up, which she might not because she’s also a Russian asset. I mean -- totally."

GABBARD DARES CLINTON TO RUN FOR PRESIDENT IN 2020, FIGHTS BACK AGAINST ASSERTIONS THAT SHE'S A RUSSIAN ASSET

Stein shot back on Friday, challenging Clinton to a one-on-one debate.

"In light of the latest slanderous allegations from @HillaryClinton, I challenge her to a debate. It's past time to give the American people the real debate they deserved in 2016, but were denied by the phony DNC/RNC-controlled Commission on Presidential Debates," Stein wrote in a series of tweets. "It's a shame HRC is peddling conspiracy theories to justify her failure instead of reflecting on real reasons Dems lost in 2016. You can slander progressives as 'Russian assets,' but you can't hide the fact that the DNC sabotaged Sanders & elevated Trump to set the stage for HRC."

She continued: "HRC's rant is Exhibit A for how the establishment is using the new Cold War to crack down on dissent & feed the war machine. Instead of addressing the crises working people face, they're painting progressives as the enemy. It's as if they're trying to lose to Trump again."

Gabbard also had a fiery response to Clinton and dared the former Secretary of State to enter the 2020 race.

"Great! Thank you @HillaryClinton. You, the queen of warmongers, embodiment of corruption, and personification of the rot that has sickened the Democratic Party for so long, have finally come out from behind the curtain," Gabbard wrote in a three-part tweet on Friday. "From the day I announced my candidacy, there has been a concerted campaign to destroy my reputation."

"We wondered who was behind it and why," Gabbard continued in her tweeted answer to Clinton. "Now we know — it was always you, through your proxies and powerful allies in the corporate media and war machine, afraid of the threat I pose. It’s now clear that this primary is between you and me.

"Don’t cowardly hide behind your proxies. Join the race directly" she said in a taunt squarely aimed at Dems' 2016 standard-bearer.

CLICK HERE FOR THE FOX NEWS APP

.

Fox News' Alex Pappas and Vadana Rambaran contributed to this report.