The United States has threatened to end electronic surveillance coordination with Britain after the government gave approval, in principle, for Chinese telecom giant Huawei to assist in building the UK’s next generation 5G data network.

Last week, Theresa May’s Conservative government agreed to allow Huawei to supply “noncore” infrastructure, in the face of US calls for a boycott of Huawei’s products. The US is hostile to any of its allies using products from Huawei, warning that this threatens NATO security and allows China critical economic dominance.

The decision was immediately condemned by Rob Joyce, a senior cyber security adviser to the US National Security Agency and a former adviser to US President Donald Trump, who said, “We are not going to give them [China] the loaded gun.”

He added of the UK’s decision, “We have got to understand all the details of that and decide what that means,” warning, “What we will be insistent on is UK decisions can’t put our information at risk, but the good news is that the UK already understands that.”

The political tension between the US and China meant that the Huawei issue had to be discussed and agreed at the UK National Security Council (NSC) last week. So secret are the NSC’s deliberations that the exact make up of its personnel is not known. It does include the prime minister and brings together cabinet ministers and senior officials involved in foreign and defence policy, as well as representatives from the intelligence agencies and the armed forces.

According to sources, the NSC was spilt down the middle over the decision to allow Huawei access, with the Guardian reporting that the “decision at Tuesday’s NSC meeting was forced through, according to one source, on the casting vote of the prime minister with a formal announcement expected later in the spring once further technical safeguards had been prepared.”

The decision was expected to remain a secret until then. But political tensions in Britain, centred on exiting the European Union (EU) and post-Brexit trade strategies amid developing trade war and mounting political instability globally, meant details of the meeting were leaked within hours to the pro-Brexit Daily Telegraph .

This was the first time that deliberations from the NSC had ever been leaked, prompting an escalation of the crisis of the already dysfunctional Tory government. The leak forced senior cabinet ministers known to be opposed to developing ties to China to issue denials that they leaked the decision. These were Home Secretary Sajid Javid, Foreign Secretary Jeremy Hunt, Defence Secretary Gavin Williamson, Development Secretary Penny Mordaunt and Trade Secretary Liam Fox. Some are considered possible candidates to replace May in the event of a leadership contest.

Cabinet Secretary Sir Mark Sedwill immediately announced an inquiry to uncover the source of the leak. It was reported that this might involve cabinet members who were present at the NSC meeting being asked to hand over their phones for examination and allowing access to their email records.

On Monday, the US stepped up its condemnation of the UK with Robert Strayer, a deputy assistant secretary at the State Department, stating that Huawei “was not a trusted vendor” and any use of its technology in 5G networks was a risk. He warned that if an ally cooperated with Huawei, the US would “have to reassess the ability for us to share information and be interconnected.”

With this, the Trump administration was making a direct threat to shut Britain out of the “Five Eyes” electronic surveillance system it leads. As well as the UK, the US is demanding that the other members, Canada, Australia and New Zealand, also exclude Huawei.

After Washington’s arm twisting, Australia and New Zealand have already blocked telecoms companies from using Huawei equipment in its 5G networks, and Canada is reviewing its relationship with the company.

These are issues of vital importance for British imperialism, following the 2016 referendum decision to leave the EU.

Writing in the Financial Times, Charles Parton, an associate fellow of the Royal United Services Institute think-tank and an adviser to Parliament’s select committee on foreign affairs, declared, “We might sleep more soundly at the decision over Huawei if we thought that our ‘Five Eyes’ allies would not cut co-operation, as the US has threatened. This alliance underpins the UK’s claims to be a global power. It is immensely important, not just for the intelligence exchanged, but for co-operation over developing methods of collecting future intelligence. The opposition of the three ministers most closely connected to the intelligence world suggests unease at the reaction of Five Eyes allies. Again, is this a risk worth taking for a Huawei system of dubious quality?”

Backing up Strayer was pro-US Tory MP Bob Seely, also a vociferous opponent of Russian President Vladimir Putin’s government in Moscow, who stated, “Robert Strayer’s remarks are common sense. Huawei cannot, by definition, be a trusted vendor. It is required by law to cooperate with Chinese secret services. It is close to, if not part of, the Chinese state.”

The Guardian noted that “sources close to Boris Johnson,” a leader of the Tories hard Brexit faction who is a favourite to succeed May, were “indicating the former foreign secretary could be willing to ‘look again’ at the Huawei approval if he were to become prime minister.”

Johnson is an outspoken supporter of the Trump administration and is demanding that the UK departs the EU in order to be free to sign free trade deals with the US and other powers globally.

However, for all the invocations of Britain stepping “out of Europe and into the world,” the Huawei fiasco makes clear that the US calls the shots. It will not countenance Britain taking actions seen as contrary to America’s geostrategic interests.

This is a major threat to the UK, which has sought deepening cooperation with China since it became a founder member of the Asian Infrastructure Investment Bank (AIIB) in 2015. That decision angered Washington, which saw the bank as a rival to the US-controlled World Bank in the Asia Pacific, but the Obama administration stopped short of threatening a break with the UK. No longer.

The NSC decision was followed a few days later by Chancellor Philip Hammond arriving in Beijing as an enthusiastic participant at the second Belt and Road Initiative forum hosted by Chinese President Xi Jinping. Hammond was among 5,000 foreign delegates from more than 150 countries, including 37 heads of government or heads of state.

Hammond declared his support for a deepening of economic ties and hailed the “truly epic ambition” of the Belt and Road Initiative—a massive infrastructure scheme aimed at linking China throughout Eurasia via land and sea, enhancing China’s global position.

A Treasury statement cited Hammond’s speech in which he declared there were opportunities for British companies in the fields of “design, engineering financing, public-private partnerships and legal services.”

He continued, “The forthcoming Economic and Financial Dialogue in June will continue the golden era of relations between China and the UK. By deepening our cooperation on financial services, trade, and investment with international partners, we can ensure Britain’s global future.”

Hammond went as far as suggesting the UK could scale back its criticism of Chinese operations in the South China Sea. This was in sharp contrast to the US’s response to the conference. Not only did President Donald Trump not attend, but there was no senior American representative at the forum. Tensions between London and Washington will inevitably escalate as a result, especially as any retreat by the UK will hand in initiative to Germany, France and other EU powers in seeking relations with Beijing.