Secretary of State Michael Pompeo warned that the U.S. may not share some information with NATO allies if they incorporate Chinese technology in their networks, his most explicit warning to date of the danger the U.S. sees in doing business with Huawei Technology Co.

“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,” Pompeo told reporters Thursday after meeting with counterparts from the North Atlantic Treaty Organization in Washington.

The U.S. campaign to steer European allies away from partnering with Huawei as they roll out 5G networks was a top priority for Pompeo during the NATO meeting, which was convened to celebrate the alliance’s 70th anniversary. So far countries including the U.K. and Germany have rebuffed the U.S. on the issue and said the threats aren’t as dire as the U.S. says.

While other U.S. officials have previously threatened to limit intelligence sharing, Pompeo himself hadn’t been so explicit in his earlier warnings. He said the U.S. has completed an assessment of the threat posed by Chinese telecommunications firms and shared it with allies.

The danger, he said, is of adopting technology from “companies so deeply connected to their own government, who would be willing to act at the behest of their government.” Officials have argued that the Chinese government could use Huawei to spy on the West.

“There is undoubtedly the risk that the U.S. will not be able to share information the same way it could if there were not Chinese systems inside of those networks,” Pompeo said.

Huawei has repeatedly denied that it helps Beijing spy on other governments or companies, and points out that no one has provided any proof to support such charges. In March the company filed a lawsuit in federal court against a statute that blocks U.S. government agencies from using its equipment.