WASHINGTON (AP) — Treasury Secretary Steven Mnuchin says the Trump administration has "very serious concerns" that the new digital currency planned by Facebook could be used for illicit activity such as money laundering, human trafficking and financing terrorism.

Mnuchin told reporters Monday at the White House: "This is indeed a national security issue." His comments came a few days after President Donald Trump tweeted that Libra (LEE'-bruh), the currency proposed by the social network giant, "will have little standing or dependability."

Mnuchin says Facebook has "a lot of work to do before we get to the point where we're comfortable with it."

His remarks came a day before Congress begins hearings on Facebook's Libra plan. The head of the Federal Reserve also raised an alarm about the plan last week.