Bitcoin prices tumbled below the $10,000-mark Wednesday alongside other cryptocurrencies as U.S. lawmakers cast doubts that they will give the nod to Facebook's (FB) - Get Report own digital coin plans, legitimizing the space in the process.

U.S. lawmakers on Tuesday grilled Facebook on its plans to introduce its own virtual currency, dubbed Libra, with David Marcus, the company's top executive overseeing the planned project, in Washington to answer questions from the Senate Banking Committee. 

The social media behemoth is pressing to get Washington onside after shocking regulators and lawmakers with its June 18 announcement of its plans to introduce its own virtual currency next year.

Bitcoin has quietly been staging a recovery this year amid expectations that the non-fiat, peer-to-peer digital currency will continue to be a payment of choice globally, and is not in imminent danger of being replaced by something else.

Facebook's Libra plan, which is seen as a major step for wider adaptation of virtual currencies, has helped stoke the bitcoin rally, as well as gains in ethereum and other digital coins.

Libra is being dubbed as "a new decentralized blockchain, a low-volatility cryptocurrency, and a smart contract platform that together aim to create a new opportunity for responsible financial services innovation" by the social media giant.

One bitcoin was trading at $9,485.17 as of early Wednesday morning, down 9.73%. Ethereum, the No. 2 virtual currency, was down 13.32% at $198.20.

Shares of Facebook were down 22 cents at $203.62 in early trading on Wednesday. They are up more than 555 so far this year.

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