President Trump on Wednesday declared a national emergency, signing an executive order that bans U.S. companies from using foreign telecom services that could pose a national security threat.

The move effectively bans companies from using Huawei, China’s largest telecom company.

Trump’s order instructs Commerce Sectary Wilbur Ross to prohibit transactions that pose an unacceptable risk to national security and the safety of U.S. citizens.

The executive order did not name any nation or company, but it has long been expected as U.S. officials have expressed concerns about China using such companies as a means for espionage.

Huawei is expected to dominate the 5G market, creating concerns that it could boost the country’s ability to spy on Americans.

“The president has made it clear that this administration will do what it takes to keep America safe and prosperous, and to protect America from foreign adversaries who are actively and increasingly creating and exploiting vulnerabilities in information and communications technology infrastructure and services in the United States,” White House press secretary Sarah Sanders said in a statement.

Last week, Secretary of State Mike Pompeo warned Britain against allowing Huawei to help build its 5G cellular network, saying the U.S. could stop sharing intelligence with the British.

“Why would anyone grant such power to a regime that has already grossly violated cyberspace?” he asked. “What can Her Majesty’s government do to make sure sensitive technologies don’t become open doors for Beijing’s spymasters?”

The U.S. has also urged other European governments to forgo working with Huawei.

The company has denied it’s a security risk.

Sen. Tom Cotton, R-Ark., praised Trump’s executive order.

“Chinese telecom companies like Huawei effectively serve as an intelligence-gathering arm of the Chinese Communist Party, and the administration is right to restrict the use of their products. Chinese components remain a Trojan horse for telecommunications infrastructure around the globe, and the Department of Commerce should deny their adoption entirely,” he said in a statement.

Another Republican, Missouri Sen. Josh Hawley, on Tuesday introduced legislation to prevent the Chinese government from obtaining sensitive American technology.

The order could escalate tensions with China amid stalled trade negotiations.