The president expressed skepticism of digital currencies in general.

“I am not a fan of Bitcoin and other Cryptocurrencies, which are not money, and whose value is highly volatile and based on thin air,” Trump wrote. “Unregulated Crypto Assets can facilitate unlawful behavior, including drug trade and other illegal activity.”

Facebook did not respond to a request for comment on Thursday night.

The company has faced questions from regulators and politicians in both parties since it announced that it planned to enter the cryptocurrency market.

Testifying before the House Financial Services Committee earlier this week, Federal Reserve Chairman Jerome Powell said the proposed coin “raises many serious concerns regarding privacy, money laundering, consumer protection and financial stability.”

Committee Chairwoman Maxine Waters expressed concern about the social-networking giant’s plans for the token and questioned Powell about the Fed’s thinking on it. Waters and others Democrats have been critical of Facebook’s strategy, and she said the company may ultimately want “to establish a parallel banking and monetary policy system to rival the dollar.”