British security officials have told telecoms operators to ensure they have adequate stockpiles of Huawei equipment owing to fears that US sanctions will disrupt the Chinese firm’s ability to maintain critical supplies, according to a letter seen by Reuters. Senior officials at the National Cyber Security Centre (NCSC), who are studying the impact of new US measures intended to restrict Huawei’s ability to source advanced microchips, wrote to BT and Vodafone last week, said three people familiar with the matter. The NCSC told the companies they needed to maintain adequate supplies of spare parts from all manufacturers, but emphasised the increased risk to Huawei’s equipment and its future ability to provide software updates for those products in the face of US pressure. “Ensuring that products and components are kept up to date is essential to maintaining the security of networks,” the letter said. “Escalating US action against Huawei may affect its ability to provide updates for products containing US technology.” An NCSC spokeswoman said: “The NCSC has provided operators with a series of precautionary steps we recommend they take while we carefully consider the impact these sanctions have on the UK’s networks.“ BT and Vodafone declined to comment. A Huawei spokesman said the company was cooperating fully with the NCSC and declined immediate further comment. Britain designated Huawei a “high-risk vendor” in January, capping its 5G involvement at a 35% market share and excluding it from the data-heavy core of the network. Officials now said they are reviewing the specific guidance on how Huawei equipment should be deployed in order to best secure UK networks and are considering a range of options. A decision is due in the coming weeks. Any move by London to further restrict Huawei or bar the company completely would strain relations with China, which have grown tense in recent months over Beijing’s handling of the situation in Hong Kong and the Covid-19 pandemic.