In a press conference Monday, Treasury Secretary Steven Mnuchin said he had several concerns regarding Facebook’s proposed cryptocurrency, Libra. During the press conference, Mnuchin stated that the digital currency “could be misused by money launderers and terrorist financiers” and that it was a “national security issue.”

“Cryptocurrencies such as bitcoin have been exploited to support billions of dollars of illicit activity like cyber crime, tax evasion, extortion, ransomware, illicit drugs and human trafficking,” Mnuchin said. He also added that he’s “not comfortable today” with Facebook’s launch. “They have a lot of work to do,” he said.

Just days prior to the press conference,  President Donald Trump tweeted on Twitter that he was “not a fan” of cryptocurrencies like bitcoin. Facebook, which plans on launching the global cryptocurrency next year, would need a bank charter to do so, according to Trump’s suggestion. Following the president’s tweet, bitcoin (BTC) dropped roughly 10% to a low of $9,872 Monday.

“The president does have concerns as it relates to bitcoin and cryptocurrencies — those are legitimate concerns that we have been working on for a long period of time,” Mnuchin said.

Facebook told CNBC in response to the Treasury secretary’s comments  that “they anticipated critical feedback from regulators, central banks, lawmakers around the world.” The social media giant claims it announced Libra a year in advance of its anticipated launch date “so that we could have those conversations.”