Buffett, who said he more often votes for Democrats but has voted for Republicans, said he disagrees with key progressive proposals, including mandatory equity ownership by employees of large, public companies. He also said he'd have no trouble voting for more moderate candidate Mike Bloomberg in the presidential election.

"I'm very much in sympathy with the fact that Senator Sanders believes that a lot of people are getting left behind and through no fault of their own," Buffett said in a CNBC " Squawk Box " interview from Omaha, Nebraska. "And there's all kinds of aspects of capitalism that need, in some ways, to be regulated. But I don't believe in giving up the capitalist system."

Berkshire Hathaway chief Warren Buffett said Monday that while he understands Sen. Bernie Sanders' motivation to ensure that no working American should have to struggle to provide for their children, he doesn't believe socialism is the answer.

Sanders, the front-runner after contests in Iowa, New Hampshire and Nevada, is a self-described democratic socialist, advocating for reforms including guaranteed employee representation on corporate boards, higher minimum wages and "Medicare for All." On Monday, he unveiled a $1.5 trillion plan to provide child care and pre-K education for all Americans over 10 years.

Asked by CNBC's Becky Quick what he makes of Sanders' success thus far, Buffett said he's still in wait-and-see mode.

"I'm a Democrat, but I'm not a card-carrying Democrat. And I've voted for Republicans and I've contributed to Republicans. In fact, I've only run for two offices in my life: one was head of the Young Republicans at the University of Pennsylvania and the other time I was actually on the ballot running for delegate at the Republican National Convention in 1960."

"But normally I vote for Democrats and we will see what happens," he added. He did, however, note that he is a card-carrying capitalist and in favor of the system as a whole.

"Everything you see is the product of a system that's worked like nothing's ever worked in the history of the world. So, I do not believe in messing up our system of developing output," Buffett continued. But "I do believe that anybody who's willing to work 40 hours a week and has a couple kids should not have to have a second job."

"I believe in having a higher income for people – not necessarily a higher minimum wage," he said. "I do not think it's at all unreasonable that the income tax credit produces at least $15 an hour, maybe higher in certain areas."

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