A former top Hillary Clinton aide took aim at 2020 presidential hopeful Sen. Bernie Sanders, I-Vt., on Friday, after Sanders said he wasn’t really interested in receiving any advice from his 2016 Democratic presidential primary rival, citing “fundamental differences” with her.

“I don’t know who our nominee is going to be but I am damn sure that beating Trump & getting America back on the right footing is going to require a unified Democratic Party, so crap like this 613 days before Election Day is irresponsible, counter-productive, & sets us all back,” former Clinton senior adviser Nick Merrill tweeted Friday.

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Merrill’s blast came after Sanders, in an appearance on ABC's “The View,” told host Meghan McCain that he didn’t think he would be meeting with Clinton for advice about his presidential bid.

“I suspect not,” Sanders said. “She has not called me.”

Sanders then explained that while he respects Clinton, they don’t exactly agree on a variety of issues.

“We have differences, you know, Hillary has played a very important role in modern American politics,” he said.

McCain reiterated, “So you’re not interested in any advice from her?”

“I think not,” Sanders said, prompting laughter from the audience as he stumbled to finish his thought. He went on to say that the two have "fundamental differences."

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Merrill said that Sanders had touted his ties to the former secretary of state when it suited him, and posted a letter from Clinton from 2016 where she thanked Sanders for campaigning for her in the final days of the 2016 campaign.

The war of words is the latest sign of lingering bad blood between the two camps. The two faced off in the 2016 Democratic presidential primary, with Sanders running a resilient challenge to the eventual nominee. Signs of trouble emerged this week when members of Clinton’s campaign criticized Sanders’ use of private jets in the last months of the campaign to Politico.

“I’m not shocked that while thousands of volunteers braved the heat and cold to knock on doors until their fingers bled in a desperate effort to stop Donald Trump, his Royal Majesty King Bernie Sanders would only deign to leave his plush D.C. office or his brand new second home on the lake if he was flown around on a cushy private jet like a billionaire master of the universe,” Zac Petkanas, who was the director of rapid response for the 2016 Clinton campaign, told Politico.

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Clinton staffers said that Sanders’ use of jets became “a running joke in the office” and noted that the use was at odds with his radical views on climate change and income inequality.

Members of Sanders’ campaign pushed back on the claims, saying that the demands were in part due to the rigorous schedule put before them, making chartered flights necessary.

“The requests for a charter only came after the schedules were put in front of us. If a less rigorous schedule were put in front of us, we wouldn’t have needed a charter and that would have been fine for everyone involved, including Bernie,” Rania Batrice, Sanders’ deputy campaign manager told the outlet. “Bernie worked his a-- off on behalf of Hillary Clinton and the campaign.”

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Michael Briggs, Sanders’ 2016 spokesman, went further and called Clinton's staff as "total ingrates.”

“You can see why she’s one of the most disliked politicians in America," Briggs said, referring to Clinton. "She’s not nice. Her people are not nice. [Sanders] busted his tail to fly all over the country to talk about why it made sense to elect Hillary Clinton and the thanks that [we] get is this kind of petty stupid sniping a couple years after the fact.”

Briggs added: “It doesn’t make me feel good to feel this way but they’re some of the biggest a--holes in American politics."

Fox News’ Brian Flood and Gregg Re contributed to this report.