U.S. says illicit activity is top cryptocurrency concern

Washington's main concern about the rise of cryptocurrencies is to make sure they are not used for illicit activity, U.S. Treasury Secretary Steven Mnuchin said on Thursday as he urged nations to join the United States in regulating them."My number-one focus on cryptocurrencies, whether that be digital currencies or bitcoin or other things, is that we want to make sure that they're not used for illicit activities," he told the World Economic Forum in Davos, Switzerland.