On Saturday, Buffett said bitcoin is " probably rat poison squared ," while Vice Chairman Charlie Munger said during the annual meeting that trading in cryptocurrencies is "just dementia."

"The asset itself is creating nothing," the Berkshire Hathaway chairman and CEO said on CNBC's " Squawk Box " from Omaha, following Berkshire's annual shareholder meeting. "When you're buying nonproductive assets, all you're counting on is the next person is going to pay you more because they're even more excited about another next person coming along."

Billionaire Warren Buffett took another swipe at bitcoin on Monday, explaining why he's shunning the cryptocurrency.

Cryptocurrencies, especially bitcoin, have become popular recently in part because of their sharp rise in prices. In 2017, bitcoin rose from less than $1,000 to more than $20,000 in some exchanges.

Still, Buffett sees them as largely speculative assets. "It's buying something because you expect the pool of people who want to buy it because they want to sell it to somebody else will grow," he said.

Bitcoin traded around $9,000 on Monday, well off last year's highs.

Buffett also compared buying bitcoin to investing in gold. "If you go back to the time of Christ, and you look at how many hours we had to give up in order to buy an ounce of gold and you bring it forward to now, you'll find the compound rate may be a tenth or two-tenths of 1 percent, … but it doesn't produce anything."

— Buffett joins "Squawk Box" for three hours, 6 a.m. ET to 9 a.m. ET, with special guests Munger and Microsoft co-founder and philanthropist Bill Gates.