The lack of transparency of stablcoins could threaten financial stability, US Federal Reserve (Fed) officials said at a meeting.
The meeting was held in late July, but its minutes have only just been released.
Participants at the meeting "stressed the fragility and general lack of transparency" of stablcoins, as well as the importance of monitoring them and developing "an appropriate regulatory framework".
"Some participants pointed to potential risks to financial stability, including those associated with the increased use of cryptocurrencies," the minutes said.
Earlier, the Fed called Tether (USDT) a "new disruptor" of the short-term lending market.
In July, Fed governor Jerome Powell questioned the need for staplecoins and cryptocurrencies following the emergence of a digital version of the dollar.