U.S. Secretary of State Mike Pompeo had that message for Britain after its decision ... To grant Huawei a role in 5G networks.
Pompeo was flying to London when he made the comments ... Warning the U.S. would ensure its data only passes through a trusted network.
Its view: putting Huawei into the system creates - quote - "real risk".
Tuesday's UK announcement grants Huawei limited access - to non-core parts of the network.
On Wednesday, prime minister Boris Johnson was defending it before parliament.
(SOUNDBITE) (English) BRITISH PRIME MINISTER, BORIS JOHNSON, SAYING: "I think it is absolutely vital that people in this country do have access to the best technology available.
But we also do absolutely nothing to imperil our relationship with the United States, to do anything to compromise our critical national security infrastructure or to do anything to imperil our extremely valuable cooperation with Five Eyes, security partners." The U.S. allegations - denied by Huawei - are that the Chinese tech giant can use its gear for spying.
Washington wants partners to ban it from 5G networks.
In a further dent to those efforts, Brussels on Wednesday resisted pressure for an outright embargo.
Instead allowing member states to decide what part Huawei can play.
The European Commission's Margrethe Vestager also warned of the 5G security challenge.
(SOUNDBITE) (English) EUROPEAN COMMISSION VICE-PRESIDENT FOR DIGITAL, MARGRETHE VESTAGER, SAYING: "Cyber-security threats, including the risk of interference by non-EU states or state-backed actors, are becoming more sophisticated and more widespread." EU governments are now advised to use several 5G providers, and not just depend on one, according to the new guidelines.