Ericsson will supply equipment for the UK's 5G network after signing a deal with BT as the telecoms firm moves ahead with plans to ditch Huawei.
Around half of the 5G traffic expected to be handled by BT and its mobile network EE will be managed by Ericsson, the companies said on Wednesday.
Nokia will supply much of the rest of the equipment, including 5G base stations and antennas, to radio sites across the UK.
Ericsson and BT's deal comes after the government in July banned Huawei from having a role in the UK's 5G network because of tough US sanctions on the Chinese firm.
Washington has long voiced concerns that Huawei's links to the Chinese military mean its involvement in crucial information infrastructure poses an unacceptable risk to national security.
British telecoms firms were told to stop purchasing new 5G equipment from Huawei by the end of this year and remove the company from the 5G network entirely by 2027.
The changes are expected to delay 5G roll-out by as much as three years and cost billions of pounds.
Ericsson's 5G Radio Access Network (RAN) connectivity will be used in UK capitals London, Edinburgh, Belfast and Cardiff, as well as other major cities.
BT's chief technology and information officer, Howard Watson, said: "In the nine months since the initial decision, we've signed significant new deals with two of the world's leading equipment vendors, Nokia and Ericsson, that will enable us not only to meet our commitments to the UK government, but to continue building out our award-winning 5G network across the UK and to consolidate our leading position in mobile.
"Two deals may not sound like a lot, but the scale and complexities involved mean that getting these agreed in just nine months is a real testament to the hard work of hundreds of people across the business."
BT had already been working with Ericsson to adopt its equipment in the sensitive "core" part of the network.
Borje Ekholm, president and chief executive of Ericsson, said: "BT has a clear direction in how it wants to drive its 5G ambitions in the UK and we are delighted to be their partner in delivering that.
"Having already been selected to partner in 5G Core, we are pleased to strengthen the relationship further with this deal that will deliver high performance and secure 5G to their customers across the UK's major cities."