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Powell says that Libra could be used for money laundering and terrorist financing, and could also threaten financial stability given that Facebook's huge user base may result in Libra's wide adoption.
Powell made the statements Wednesday at a House Financial Services Committee hearing.
"The process of addressing these concerns should be a patient and careful one," Powell says in response to questions from Rep. Maxine Waters, the California Democrat who chairs the House Financial Services Committee.
Powell also says the Fed is coordinating with other regulators, such as the Treasury Department, and other central banks overseas.