Vodafone and BT said they would need a minimum of five years to remove equipment made by Huawei from their British networks, with Vodafone putting the cost of doing so in the "single figure billions" of pounds range.
Andrea Dona, head of networks Vodafone UK, told a committee of lawmakers the operator needed to have a "sensible time scale" of several years to implement any further Huawei restrictions, with a minimum transitional plan spanning five years.
Rival BT told the same committee it needed a minimum of five years, and ideally seven, to remove Huawei from its network.
BT was already trialing switching some network sites from Huawei to other vendors, its chief technology officer Howard Watson said.
Britain granted Huawei a limited role in its future 5G networks in January, but ministers have since said the introduction of US sanctions could have a significant impact on its ability to securely supply crucial pieces of networking equipment.
As a result, Britain is again reviewing what role Huawei should play in its telecom networks. Huawei told the same committee it was too early to quantify what impact the sanctions would have on its operations, and no hasty decisions should be made.
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