BT chief executive Philip Jansen has urged the British government not to move too fast to ban China's Huawei from the 5G network.
The BT CEO has cautioned that there could be outages and even security issues if it did.
British Prime Minister Boris Johnson is due to decide this week whether to impose tougher restrictions on Huawei, after intense pressure from the US to ban the Chinese telecoms giant from Western 5G networks.
Boris Johnson in January defied President Donald Trump and 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 mood in London.
"If you are to try not to have Huawei at all, ideally we would want seven years and we could probably do it in five," BT CEO Jansen told BBC radio.
Asked what the risks would be if telecoms operators were told to do it in less than five years, Jansen said: "We need to make sure that any change of direction does not lead to more risk in the short term."
"If we get to a situation where things need to go very, very fast, then you are into a situation where potentially service for 24 million BT Group mobile customers is put into question - outages," he said.
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 the geopolitics of the 21st century.
The US says Huawei is an agent of the Chinese Communist State 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.
Meanwhile, Huawei Technologies has requested a meeting with UK Prime Minister Boris Johnson to work out a deal to delay its potential removal from the country's 5G phone network, the Sunday Times newspaper said.
The Chinese telecoms equipment maker is seeking to delay its removal from the UK's 5G telecoms networks until after elections in June 2025, in the expectation that the new government may reverse the decision, the newspaper reported.
Huawei will in return pledge to maintain its equipment in the UK, which is also used in the 2G, 3G and 4G networks, the report added.
Britain granted Huawei a limited role in its future 5G networks in January, but ministers have since said the introduction of US sanctions on the company means it may no longer be a reliable supplier.
Boris Johnson has faced intense pressure from the US and some British politicians to ban the telecommunications equipment maker on security grounds.
China's ambassador to London, Liu Xiaoming, warned last week that getting rid of Huawei would send a "very bad message" to Chinese business.
A government update on the Chinese company is expected to be published before July 22, according to a government minister and official.