BT has signed a deal to use Ericsson's 5G radio antennas, base stations and other equipment to upgrade its EE mobile network.
BT said in time it expected 50% of all its 5G traffic to be transmitted via the Swedish company's kit.
The move will let it ditch Huawei without becoming totally dependent on its other radio access network (Ran) equipment provider, Nokia.
It follows a government ban of the Chinese company's products.
Ministers announced in July that all the UK's mobile providers must stop buying new Huawei 5G telecoms infrastructure after 31 December, and must also remove any of its 5G equipment purchased before that date by 2027.
This was a result of sanctions imposed by Washington, which claims Huawei poses a national security threat - something the company denies.
BT is already in the process of using Ericsson products to replace Huawei's equipment in its "core" - the most sensitive parts of its network that route data and voice calls across computer servers to get them to the right destination.
Huawei released a report earlier on Wednesday, claiming its UK ban could cost thousands of jobs and billions of pounds of lost economic benefits as a result of the 5G rollout taking longer to complete.
The latest announcement had been widely expected, as BT and other mobile network providers typically use two Ran equipment vendors. This allows them to maintain a service if a problem develops in one of the provider's systems, while still enjoying efficiency savings from not having to maintain and install a wider range of products.
Other companies, including NEC and Samsung, are also active in the sector. But it would have been more complicated to have tried to integrate their solutions.
Some industry leaders have privately expressed concern that Huawei's exit from the market could reduce competition, resulting in the 5G upgrade becoming more expensive.
But in the longer term, another solution known as OpenRan is being explored.
This refers to a plan to eventually standardise the hardware used in radio access networks so that one supplier can be switched for another via software alone. This would avoid the need to rip out one firm's customised equipment and replace it with another's.
Source: BBC