A number of U.S. lawmakers said Facebook cannot be trusted to manage cryptocurrencies and urged the social media giant to immediately halt a small pilot trial of its cryptocurrency wallet called Novi, which launched last Tuesday.

U.S. Democratic senators expressed opposition to the tech giant’s two-year-old efforts to manage a cryptocurrency and digital wallet.

“Facebook cannot be trusted to manage a payment system or digital currency when its existing ability to manage risks and keep consumers safe has proven wholly insufficient,” the senators wrote.

The senators’ letter shows that even Facebook’s small pilot of its cryptocurrency is under scrutiny by lawmakers and regulators who have previously expressed antitrust concerns.

Facebook launched a cryptocurrency project in June 2019 to expand into e-commerce and global payments.

However, the project was immediately met with strong opposition from policymakers around the world, who feared that it would lose control of the money system, encourage crime and compromise users’ privacy.

The project was renamed last December in a renewed attempt to win regulatory approval, and its scope was expanded to include a single dollar-backed digital coin.

A Novi spokesperson said the company was looking forward to responding to the committee’s letter.