In a new letter sent to Facebook executives, US lawmakers are officially asking the social networking giant to cease all development of its Libra cryptocurrency, the media has reported.

Under Facebook subsidiary Calibra, the social networking giant has planned to introduce a digital wallet for Libra. The wallet will be available on Messenger, Whatsapp and as a standalone app and is expected to be launched in 2020.

Representative Maxine Waters (D-CA), the chairwoman of the House Financial Services Committee, hinted at a move like this in June, shortly after the project was announced.

Waters' letter, sent to Facebook CEO Mark Zuckerberg, Chief Operating Officer Sheryl Sandberg and Calibra CEO David Marcus, formalizes that request from a few weeks ago. Besides Waters, the letter is signed by House Finance's subcommittee leaders, The Verge reported on Tuesday.

According to reports, Waters has repeatedly called on the social networking giant to pause development of Libra, though this is the first time she has done so as part of a formal letter to the company.

Facebook has tied up with 27 organisations around the world to start the non-profit Libra Association to create the new currency.