Vodafone and BT said it would take at least five years to remove Huawei devices from their UK networks, with Vodafone putting the cost in the "single-digit billion" pound range.
Andrea Dona, head of the Vodafone UK network, told a legislature committee that the operator needed a "reasonable time scale" of several years to implement further Huawei restrictions with a minimum transition plan of five years.
Rival BT informed the same committee that it would take at least five and ideally seven years to remove Huawei from its network.
BT has already attempted to move some of Huawei's network locations to other vendors, said Howard Watson, chief technology officer.
The UK gave Huawei a limited role in its future 5G networks in January, but ministers have since said that the imposition of U.S. sanctions could have a significant impact on its ability to safely secure key network devices.
As a result, the UK is reviewing what role Huawei should play in its telecommunications networks. Huawei told the same committee that it was too early to quantify the impact the sanctions would have on its business and no rash decisions should be made.
(Except for the headline, this story was not edited by NDTV staff and published from a syndicated feed.)