When UK Prime Minister Boris Johnson announced in January that he would allow China’s largest telecom company to have a limited role in erecting a 5G wireless network for his country, the US warned that there would be serious consequences. President Donald Trump has now directed his administration to figure out exactly what they might be. The National Security Council has launched an interagency review to determine what military and intelligence assets need to be removed from the UK if Huawei participates in building the 5G network, according to US officials. The dispute between the two allies comes down to whether a country can truly mitigate the intelligence threat posed by a Chinese company that has the ability to beam back data from its wireless network to the Chinese government. Johnson has said the UK can, by barring Huawei equipment from base stations near sensitive military and intelligence sites and capping the company’s overall participation in the 5G network. US officials don’t believe these assurances. As Secretary of Defense Mark Esper told Congress last week: “If our NATO allies incorporate Huawei technology, it may very well have a severe impact on our ability to share information, to share intelligence, to share operational plans and for the alliance to conduct itself as an alliance.” One senior US official working on Huawei policy told me that one of the purposes of the interagency review was to take an inventory of US equipment and bases in the UK and evaluate the risks of keeping them there. As this official said, the US needs to assess the impact of “putting smart antennas and computers run by the Chinese Communist Party all over our closest ally.” Another source familiar with the review told me that the US intention is not to punish the UK for letting Huawei into its 5G wireless network, but rather to take precautions against allowing China access to some of America’s most sensitive technology and secrets. Whatever the intention, the UK has a lot to lose if the US can no longer trust that its most sensitive intelligence and military programs can be protected from China’s prying digital eyes. For example, the UK hosts the NSA’s largest overseas base at Menweth Hill, which was essential in combing through electronic data used by the US military and CIA to target the locations of foreign terrorists. According to a 2016 story in the Intercept, that base contains powerful antennae that can intercept signals between foreign satellites. It can also use US satellites hovering above foreign countries to monitor wireless traffic below. The Huawei decision has already disrupted some plans for basing US equipment in the UK. The US is scheduled to send sensitive RC-135 surveillance planes to Royal Airforce Base Fairford by 2024. One Senate staffer told me these shipments may be on hold for now. Bloomberg