LONDON  — Britain decided Tuesday to give Huawei limited access to build parts of its new high-speed mobile network, in a setback for the U.S., which has been pushing allies to ban the Chinese company.

The government said it is excluding “high risk” companies from supplying the sensitive “core” parts of the new fifth-generation, or 5G, networks. But it will allow high risk suppliers to provide up to 35% of the less risky radio access network.

The announcement did not mention any companies by name but said “high risk vendors are those who pose greater security and resilience risks to U.K. telecoms networks” - a clear reference to Huawei.

The United States claims that China’s communist leaders could, under a 2017 national intelligence law, compel Huawei to carry out cyberespionage. Huawei denies that would be possible.

The 5G infrastructure program is seen as being critical to Britain’s economic future as the country leaves the European Union. But the decision is fraught, as the United States objects to allowing Huawei to provide vital infrastructure and has threatened to cut off intelligence sharing with allies that do use Huawei.

The British government said Tuesday after a meeting of its National Security Council that it is taking some steps that will allow it “to mitigate the potential risk posed by the supply chain and to combat the range of threats, whether cyber criminals, or state sponsored attacks.″

The decision is awkward for the government of British Prime Minister Boris Johnson, as he risks the fury of one of Britain’s closest allies at just the moment it really needs Trump’s administration to quickly strike a trade deal after Brexit. Britain is also loathe to insult China, which it likewise needs for future trade deals.

Huawei said it was “reassured” by the British government’s decision.

“This evidence-based decision will result in a more advanced, more secure and more cost-effective telecoms infrastructure that is fit for the future,” Vice-President Victor Zhang said. “It gives the U.K. access to world-leading technology and ensures a competitive market.”

The measures also include keeping Huawei out of all “safety related and safety critical networks” and banning it from sensitive places such as nuclear sites and military bases.