The UK could see internet "outages" if it moves too quickly ripping Huawei from its 5G network, BT's boss has warned.
Philip Jansen, chief executive of the telecoms giant, said the industry would need at least five years - and ideally seven - to extract the Chinese firm from its infrastructure if ordered by the government to do so.
“If we get in a situation where things need to go very fast, then we go into a situation where service for 24 million BT Group mobile customers is put into question - outages would be possible," Mr Jansen told the BBC's Today programme.
Boris Johnson is due to decide this week whether to impose tougher restrictions on Huawei, after intense pressure from the US to ban it from Western 5G networks.
The prime minister in January defied US president Donald Trump when he granted Huawei a limited role in the 5G network, but the perception that China did not tell the whole truth over the coronavirus crisis and a row over Hong Kong has changed the political mood in London.
“We always, at BT and in our discussions with GCHQ, we always take the (view) that security is paramount; it is our number-one priority," Mr Jansen said.
”But we need to make sure that any change of direction doesn't lead to more risk in the short-term - I think that's where the detail really matters."
He added: "The security and safety in the short-term could be put at risk - this is really critical here.
“If you are not able to buy or transact with Huawei that would mean you wouldn't be able to get software upgrades if you take it to its specificity.”
In what some have compared to the Cold War antagonism with the Soviet Union, the US is worried that 5G dominance is a milestone towards Chinese technological supremacy that could define geopolitics for the 21st century.
Washington says Huawei is an agent of the Chinese Communist Party and cannot be trusted.
Huawei, the world's biggest producer of telecoms equipment, has said the US wants to frustrate its growth because no US company could offer the same range of technology at a competitive price.
Additional reporting by Reuters