Lawmakers in Washington and London have ratcheted up the pressure on Boris Johnson to stop China's Huawei from supplying kit for the UK's fifth-generation mobile phone network.
But the prime minister's national security council is on Tuesday expected to grant Huawei a restricted role providing equipment for the 5G data infrastructure.
Mr Johnson is seeking to balance the consumer and economic benefits of a fast rollout of 5G using Huawei equipment against national security concerns about the Chinese telecoms equipment maker raised by the Trump administration as well as lawmakers in Washington and London.
The prime minister insisted the national security council could deliver "a very, very important strategic win for the UK" - hinting that he would follow advice from British officials by giving Huawei a role in supplying "non-core" elements of the 5G network.
Mr Johnson is also expected to impose a market share cap on Huawei, in an attempt to reassure the Trump administration that Britain does not want to be reliant on Chinese technology and would like western companies to build up their own 5G capabilities.
Speaking at King's College London, Mr Johnson said: "There's no reason why we shouldn't have technological progress here in the UK, allow consumers, businesses in the UK to have access to fantastic technology, fantastic communications, but also protect our security interests and protect our key partnerships with other security powers around the world."
Priti Patel, the home secretary, and defence secretary Ben Wallace are opposed to Huawei but are outnumbered on the nine-member national security council.
Huawei has consistently said it is a private company and is not subject to state interference, but Conservative and Labour MPs lined up in the House of Commons on Monday to say it represented a risk to Britain's security.
Tom Tugendhat, a senior Conservative MP, said Mr Johnson was about to "nest a dragon into our critical national infrastructure". Former Tory leader Iain Duncan Smith said such a decision would be "bizarre".
Three senior US senators wrote on Tuesday to all members of Mr Johnson's national security council urging them to exclude Huawei, arguing that the company's inclusion gave an economic advantage to one of China's national champions.
Marco Rubio, Tom Cotton and John Cornyn, all Republicans, said: "The more countries do not allow Huawei to participate in their 5G networks, the more market space there is for innovators and entrepreneurs to develop competing products. And these incentives are already starting to bear fruit."
The letter highlights a change in strategy from Washington, where Trump administration officials believe economic arguments will probably carry more weight in London than national security ones.
British officials have said they can manage any security risk around Huawei kit if it is not part of the 5G network "core", and that it will not have a negative impact on intelligence sharing with Washington.
Core parts of the network refers to servers and systems where mobile operators' customer information is processed. Non-core elements include antennas and base stations that sit on masts and rooftops.
The UK's four mobile network operators - EE, O2, Three and Vodafone - have launched 5G services over the past six months, all involving some Huawei equipment. The national security council's decision relates to whether Huawei should have an ongoing role as a supplier.
The US has been looking for ways to incentivise Huawei's rivals, including Ericsson, Nokia and Samsung, and is hoping it can leverage its allies' support.
Members of the Trump administration are backing a new technology known as the "open radio access network" (*), which could supplant Huawei's 5G kit and price advantage. But industry executives warn it is some years away.
The proposed UK cap on market share is seen by the telecoms sector as an additional safeguard that will ensure no city or region is dominated by Huawei equipment.
If the threshold is limited to 5G kit, then complying with a cap pitched between 35 per cent to 50 per cent of all radio equipment in a specific region would require some Huawei base stations to be swapped out for equivalent Ericsson or Nokia gear over time.
UK intelligence officials believe their US counterparts are more relaxed about the possibility of Mr Johnson using Huawei's 5G equipment than the White House.
Peter Ricketts, the former UK national security adviser, said that regardless of political warnings made about intelligence sharing, operational ties between UK and US spy agencies were deep.
(*) A radio access network (RAN) is part of a mobile telecommunication system. It implements a radio access technology. Conceptually, it resides between a device such as a mobile phone, a computer, or any remotely controlled machine and provides connection with its core network (CN). Depending on the standard, mobile phones and other wireless connected devices are varyingly known as user equipment (UE), terminal equipment, mobile station (MS), etc. RAN functionality is typically provided by a silicon chip residing in both the core network as well as the user equipments.
O-RAN - is an open RAN network meaning that any vendor's equipment would work on any part of the network regardless of whose core was managing the network.
Open, standards-based network architectures with interoperable interfaces and off-the-shelf components enable mobile operators to address a diverse set of demands in support of new vertical market revenue opportunities.
simply OpenRAN is an initiative to define and build 2G, 3G and 4G RAN solutions based on a general-purpose vendor-neutral hardware and software-defined technology.