Two U.S. Senators have publicly asked Visa, Stripe, and Mastercard to remove themselves from the Facebook-led cryptocurrency payment network, Libra.

Senator Brian Schatz (D-HI) and Sherrod Brown (D-OH) sent three separate letters Tuesday to Visa CEO Alfred F. Kelly Jr., Stripe CEO Patrick Collinson and Mastercard CEO and president Ajaypal Singh Banga over the firms’ participation in the developing network. The three companies are among 27 partners for the project so far.

Earlier this month PayPal dropped out of the Libra Association, just weeks before members are to sign a formal charter on Oct. 14.

In the letters, Schatz and Brown say Facebook, the driving force behind the network, has failed to satisfactorily answer regulatory concerns over terrorism, money laundering, monetary policy and economic destabilization.

At the heart of the senators’ argument lay past accusations against the social media giant such as a New York Times article exposing criminal abuse of Facebook’s messenger app.

The letter states:

“It is chilling to think what could happen if Facebook combines encrypted messaging with embedded anonymous global payments via Libra.”

In what could be viewed as threatening language, Schatz and Brown say participating firms such as Visa, Stripe, and Mastercard may see heightened regulatory scrutiny overall as a result of Libra membership.

“If you take this on, you can expect a high level of scrutiny from regulators not only on Libra-related payment activities, but on all payment activities,” they wrote.

Libra image via Shutterstock