Billionaire investor Warren Buffett on Monday said former Secretary of State Hillary Clinton Hillary Diane Rodham ClintonWhat Senate Republicans have said about election-year Supreme Court vacancies Bipartisan praise pours in after Ginsburg's death Trump carries on with rally, unaware of Ginsburg's death MORE will "very likely" be president, adding that Sen. Elizabeth Warren Elizabeth WarrenBiden's fiscal program: What is the likely market impact? Warren, Schumer introduce plan for next president to cancel ,000 in student debt The Hill's 12:30 Report - Presented by Facebook - Don't expect a government check anytime soon MORE's (D-Mass.) "angry" political rhetoric is a “mistake.”

"[Clinton is] extremely likely to be the Democratic nominee, and I think she's very likely to be the president of the United States," Buffett said on CNBC's "Squawk Box.”

When asked to comment on Warren, he said that "she would do better if she was less angry and demonized less."

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"I believe in ‘hate the sin but love the sinner.’ I also believe in praising by name and criticizing by category and I'm not sure that I've totally convinced Elizabeth Warren that's the way to go," Buffett told CNBC. "It's a mistake to get angry with people that disagree with you. In the end, we do have to work together."

Buffett, who has supported Democrats in the past, joins other Democrats who have increasingly criticized Warren for her aggressive political tone. Warren frequently attacks big businesses and has said the economy is "rigged" against the working class.

Warren and the Obama administration frequently speak highly of Buffett's tax proposal, which would require wealthy Americans to pay higher taxes than the rest of the country.

"I think the whole nature of governing — particularly when you have divided government like we have now — is you end up with bills that each side doesn't like. But they like it better than doing nothing," Buffett said. "That's the way government has to function. It does not help when you demonize or get too violent with the people you're talking to."

Despite his political rhetoric, Buffett reiterated that he is "not a card-carrying Democrat."

"I vote Democrat most of the time. I agree with their position on social matters to a very significant degree," Buffett said on CNBC. "But I'm not a straight-down-the-road Democrat."

Buffett also said that he supports construction of the Keystone XL pipeline, which many progressives oppose due to environmental concerns. President Obama vetoed legislation that would have approved the pipeline.