"I get into enough trouble with things I think I know something about," he added. "Why in the world should I take a long or short position in something I don't know anything about."
Exchange operators such as CME Group and Cboe Global Markets have opened their platforms to allow bitcoin futures bet365 trading.
The price of bitcoin declined 3.69 percent to $13,907 Wednesday, according to data from industry website CoinDesk. The digital currency is up more than 1,500 percent in the past 12 months.
Buffett's comments came a day after Chairman and CEO Jamie Dimon backpedaled his earlier criticisms of cryptocurrencies. In September, Dimon called bitcoin a fraud.
—Reuters contributed to this report.
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