5G refers to the fifth, most advanced generation of wireless telecommunications systems; its peak speed is supposed to be 100 times faster than 4G. Countries around the world have been diving into this promising technology, but the US has raised concerns over the involvement of China's telecom giant Huawei in building national 5G networks.

Washington officials are said to be considering an attempt to dissuade UK Prime Minister Theresa May from letting Huawei take part in building her country's future 5G mobile phone network.

"We have our concerns and we continue to engage with the UK government on the issue," the Daily Mail cited a US government source as saying.

It comes on the heels of reports that the UK National Security Council, which includes Theresa May and some of her cabinet ministers, has allowed Huawei to build "non-core" infrastructure for the 5G network, while banning it from supplying core components.

This decision was met with mixed reactions; the chairman of Britain's Foreign Affairs Committee, for instance, warned that it's hard to draw a line between core and non-core in 5G, while some Conservative MPs are reportedlylooking to overturn May's move.

Huawei has recently faced allegations that it is linked to Chinese authorities and even has been spying on their behalf, although the company insists it is independent from the government. A new report claims that US foreign intelligence officials believe Huawei is sponsored by China's military, and that the country's Ministry of State Security has allegedly approved government funding for the tech giant.

Last year, the United States, Australia, Japan, and New Zealand all banned Huawei from participating in government contracts, citing security reasons, while several other countries said they were also worried about Huawei's activities.

The United States has also been pushing for the European Union not to use Huawei's gear in 5G networks over concerns that it would open citizens and governments up to espionage and other forms of cyber-attacks. Germany, however, has refused to ban Huawei from its recent auction for building its 5G network.

US envoy to Germany Grenell has warned that Washington would scale down intelligence cooperation with Berlin, should the latter allow the Chinese company to take part in the project. German Foreign Minister Heiko Maas issued the sharpest rebuke yet in March when he said Berlin would not tolerate blackmail.