London: Two of Theresa May's national security ministers have warned Boris Johnson against greenlighting Huawei involvement in the country's 5G rollout as the Prime Minister appears poised to do on Tuesday.

On his way to Britain: US Secretary of State Mike Pompeo. Credit:AP

The warnings from former foreign and defence secretaries came as the US Secretary Mike Pompeo warned the British they could not call themselves a sovereign nation if they allowed Huawei in.

Sovereignty was a key rallying cry of the Vote Leave campaign during the EU referendum, which Johnson headed. Pompeo is due to arrive in London on Wednesday, potentially setting up explosive scenes, if the National Security Council (NSC) decides on Tuesday to allow Huawei to supply masts and antennas.

The decision is nearly 12 months overdue because the last time the Conservative government debated the issue, the NSC split on the decision which was sensationally leaked, leading to the sacking of the then Defence Secretary Gavin Williamson.