On Tuesday, the head of Goldman Sachs joined the fray of Wall Street leaders to comment on digital currency bitcoin — and he's undecided.

I'm "still thinking about #Bitcoin," Lloyd Blankfein, chairman and CEO of Goldman Sachs, said in a tweet. I have "no conclusion. [I'm] not endorsing/rejecting."

I "know that folks also were skeptical when paper money displaced gold," Blankfein said.

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On Monday, Goldman Sachs said in response to client interest, it is exploring a new trading operation focused on bitcoin and other digital currencies.

Earlier Tuesday, BlackRock Chairman and CEO Larry Fink said the growth of digital currencies reflects speculation from Asian investors and money laundering.

Last month, JPMorgan Chase CEO Jamie Dimon called bitcoin a "fraud" that "won't end well."

Morgan Stanley CEO James Gorman took the other side and said cryptocurrencies are "certainly something more than just a fad" and have "a sort of government risk factor."