Some European countries could soon find themselves cut off from U.S. intelligence and other critical information if they continue to cultivate relationships with Chinese technology firms.
U.S. Secretary of State Mike Pompeo issued the warning Thursday, following a meeting of NATO foreign ministers in Washington.
"We've done our risk analysis," Pompeo said. "We have now shared that with our NATO partners, with countries all around the world. We've made clear that if the risk exceeds the threshold for the United States, we simply won't be able to share that information any longer."
U.S. defense and intelligence officials have warned repeatedly in recent years of a growing threat that information shared over Chinese-built networks or Chinese-made devices could be stolen or copied and shared with the Chinese government.
More recently, concerns have focused on China's Huawei and ZTE, which have been offering to build advanced, high-speed 5G for mobile devices across Europe.
A report issued earlier this week by the U.S. Defense Innovation Board, which advises the Pentagon, raised the possibility Huawei already is building so-called "backdoors," or security vulnerabilities, into its software and products.
"Many of these seem to be related to requirements from the Chinese intelligence community pressuring companies to exfiltrate information about domestic users," the report said, citing the example of Xiongmai, a Chinese security camera maker that was using Huawei code to allow unauthorized access to millions of cameras.
While some European countries have acknowledged U.S. concerns, the European Union has rejected calls for a blanket ban on Huawei, in particular.
As for NATO, some officials, including Secretary-General Jens Stoltenberg, have called for more consultations and have suggested the need for a more nuanced response, given there are currently few alternatives in Europe to Huawei's 5G technology.
"We're just in the preliminary stages," NATO analyst and consultant Benedetta Berti said earlier this week in Washington.
"We need to take stock of our critical vulnerabilities, of the impact of external investments on our critical infrastructure," she said. "We will come to a common strategic understanding."
But U.S. officials are pushing for greater urgency.
"It is as important for NATO as it is for us," State Department Director of Policy Planning Kiron Skinner told reporters this week. "How European countries address China's involvement across all of their sectors is central to American security," he added.
"When a nation shows up and offers you goods that are well below market, one ought to ask what else is at play," Pompeo said Thursday, calling the offers from Chinese technology companies "literally too good to be true."
"There is undoubtedly the risk that NATO or the United States will not be able to share information in the same way it could if there were not Chinese systems inside of those networks, inside of those capabilities," he said.
WATCH: US, China, NATO