The firm said a number of issues, from acquiring the right planning permissions from landlords to arranging 5G equipment on masts, had forced it to push its original target “slightly behind”.
Three became the third of the four big UK networks to launch 5G in August, but only as a home broadband service across parts of London.
It had originally planned to expand its 5G footprint to 25 towns and cities by the end of 2019, which included Birmingham, Brighton, Bristol, Cardiff, Edinburgh, Glasgow, Leeds, Liverpool, Manchester, Nottingham, Sheffield and Sunderland.
“There are a number of parts we need to put in place to deliver our 5G experience: 5G equipment on masts, the right backhaul transmission, as well as the need to acquire the right planning permissions from landlords,” the company said.
“Added to this, we also need to move all of our customer traffic on to the world’s first 5G cloud core network.
“Some of these components are more time consuming and complex than others, and, as a result, our 5G rollout is slightly behind our original plan.”
The telecommunications giant has not revealed a revised timescale for the rollout.
Rival EE launched its 5G offering in May, followed by Vodafone in July and O2 in October.