"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 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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