President Donald Trump has declared a national emergency to protect US computer networks from "foreign adversaries".
Donald Trump Photo: AFP / Saul Loeb
The president signed an executive order which effectively bars US companies from using foreign telecoms believed to pose a security risk to the country.
Mr Trump does not name any company specifically in the order.
However, analysts suggest it is mainly directed at Chinese telecommunications giant Huawei.
A number of countries - including the US - have raised concerns that the company's products could be used by China for surveillance. Huawei has said its work does not pose any threat.
According to a White House statement, Mr Trump's order aims to "protect America from foreign adversaries who are actively and increasingly creating and exploiting vulnerabilities in information and communications technology infrastructure and services".
It gives the secretary of commerce the power to "prohibit transactions posing an unacceptable risk to the national security", the statement adds.
The move was instantly welcomed by Federal Communications Commission Chairman Ajit Pai, who said in a statement it was "a significant step toward securing America's networks".
The US had already restricted federal agencies from using Huawei products and has encouraged allies to shun them, while Australia has blocked the use of Huawei gear in next-generation 5G mobile networks. New Zealand's Government Communications Security Bureau (GCSB) turned down Spark's proposed use of Huawei equipment in its 5G network because it says it would raise significant national security risks.
Meanwhile, Huawei chairman Liang Hua said it was "willing to sign no-spy agreements with governments" during a meeting in London on Tuesday, as concerns over the security of its products used in next-generation 5G mobile networks continued to grow.
Mr Trump's latest move is also likely to inflame relations with China, which are already under strain as the two engage in a trade war.
The US more than doubled tariffs on $US200bn of Chinese goods on Friday and China retaliated with its own tariff hikes on US products.
This escalated the situation which only recently seemed to be nearing a conclusion.
- BBC