Amid a deepening trade war with China, President Trump on Wednesday declared a “national emergency” to protect U.S. communications networks in a move that gives the federal government broad powers to bar American companies from doing business with certain foreign suppliers — including the Chinese firm Huawei.

Trump declared the emergency in the form of an executive order that says foreign adversaries are exploiting vulnerabilities in U.S. telecom technology and services. It singles out economic and industrial espionage as areas of particular concern.

The order authorizes the commerce secretary to block transactions involving communications technologies built by firms controlled by a foreign adversary that puts U.S. security at “unacceptable” risk — or poses a threat of espionage or sabotage to networks that underpin the day-to-day running of vital public services.