President Donald Trump on Wednesday signed an executive order declaring a national emergency and barring US companies from using telecommunications equipment made by firms posing a national security risk.
The executive order invokes the International Emergency Economic Powers Act, which gives the president the authority to regulate commerce in response to a national emergency that threatens the United States.
No countries or companies are mentioned in the order, but the move comes amid growing tensions between Washington and China and some of its major technology and telecommunications companies.
It could be aimed at Chinese tech giant Huawei, the world's biggest supplier of network equipment used by phone and internet companies. Huawei has long been seen as a front for spying by the Chinese military or security services, but the company has denied the allegations.
Under the order, Trump will be able to stop foreign tech firms from trading in the U.S., which could block Huawei's U.S. business interests. The U.S. government has already banned Huawei phones from military bases as well as the use of some Huawei telecommunications equipment.
Huawei's chief financial officer, Meng Wanzhou, was arrested in Canada in December The U.S. is seeking to extradite her to face charges of violating U.S. sanctions.