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.