Top British officials apparently have decided to let the Chinese technology giant Huawei help develop an ultra-fast 5G wireless network in the United Kingdom, according to reports, in spite of pressure by U.S. officials to freeze out the company on security grounds.

The leak of the apparent decision by Britain’s National Security Council — a panel led by Prime Minister Theresa May — risks inflaming tensions between the U.K. and the Trump administration as Huawei flexes its muscles as the world’s dominant supplier of telecom equipment. And it instantly created a political firestorm among members of Parliament determined to hunt down the source of the leak.

Any decision to move forward with Huawei will not be official until it is announced by the secretary for digital culture and reported to Parliament. And one senior official said that deliberations are still ongoing. But any council conclusion to let Huawei participate, even in a limited way, in Britain’s 5G rollout would be a significant diplomatic defeat and raise the security risks for the United States, whose networks connect with Britain’s and which has argued that Huawei’s networking equipment cannot be trusted — and could be used for spying purposes or to disrupt networks.

Following the reports, White House national security council spokesman Garrett Marquis said on Twitter that the Trump administration is continuing to work “across government & with allies & partners to mitigate risk in the deployment of communications infrastructure.”

He added: “As the President has said, ‘5G networks must be secure. They must be strong. They have to be guarded from the enemy-we do have enemies out there…’”

Some analysts said that such a decision would set a precedent that other countries would be likely to follow.

Countries would be "less likely to do a complete ban,” said James Lewis, a cyber policy expert at the Center for Strategic and International Studies who has followed the international 5G debate closely.

Lewis said it was still possible that the British decision, when it is announced, could reduce risk to a manageable level. “If the British implement their restrictions in a tough way, it’s not a big deal. If they implement them in a soft way, then Huawei will be all over the network,” he said.

For instance, Huawei will continue to be barred, as it is in the 4G networks, from the “core” of Britain’s 5G network, which contains routers and switches handling massive volumes of traffic, officials said. The limitations are also expected to include geographic restrictions near sensitive networks.

But a number of experts do not believe such restrictions will be sufficient.

Malcolm Turnbull, Australia’s former prime minister, said that even if Huawei is limited to the network “edge," or where radio antennae connect with user devices, the risk is still there.

“With 5G we have had to recognize that the core/edge distinction no longer exists,” Turnbull said in a speech in New York on Thursday. That is why Australia last year became the first nation to put in place new requirements on “high risk” vendors that effectively banned Huawei from the country’s 5G network. Such vendors, the government determined, could be subject to directions from foreign intelligence services to act contrary to national security.

“Our decision was not taken lightly” or based on “near term threats,” he said. Rather, it was “a long-term prudent hedge.”

Reports indicated that several members of the security council, including the home, foreign and defense secretaries, had expressed reservations about the plan. Britain’s GCHQ intelligence service last month delivered a scathing assessment of Huawei security risks in the 4G networks. But, according to British press reports, May gave the green light.

The apparent decision was first reported by The Daily Telegraph on Wednesday after May and other ministers on the council met to discuss Huawei’s possible role in the 5G network.

5G proponents say the wireless technology will lead to mobile download speeds up to 100 times faster than what is found on the 4G LTE in many smartphones today. And, they say, it will pave the way for future technologies such as self-driving cars and a world of networked, smart appliances. The United States is racing against other countries to get a critical mass of consumers connected to 5G, in hopes that U.S. businesses will be the ones to create the Uber and Spotify of the future.

Huawei celebrated the reports, tweeting: “5G means 5G: British PM Theresa May defies U.S. instructions to ban Huawei by granting the Chinese tech giant access to its 5G network. #HuaweiFacts.”

The leak came in a week in which Huawei’s dominance of the global 5G equipment market was made clear by the Chinese company’s first-ever quarterly earnings report, announcing revenues of $26.7 billion — a 39 percent increase over the same time last year — and promising “a year of large-scale deployment of 5G around the world.”

The company said Monday it has signed 40 deals with wireless carriers to provide 5G equipment so far and has shipped more than 70,000 5G base stations — the sophisticated radios that allow 5G cell sites to communicate with mobile devices. Huawei had previously issued financial updates only twice a year.

Huawei’s results far outstripped those of its closest competitors — Finland’s Nokia, which reported revenues of $5.7 billion for the quarter, and Sweden’s Ericsson, with $5.1 billion. On his company’s earnings call, Nokia chief executive Rajeev Suri acknowledged that the firm faced “a weak quarter.” Together, the three companies account for a majority of the global telecom equipment market. There are no U.S. manufacturers of 5G wireless gear.

In Europe, Huawei already has a substantial presence in the continent’s 4G networks. The firm has not built its gear to be “interoperable” or easily meshed with other companies’ equipment. If a telecom company wants to replace Huawei gear, it must rip it out and install new equipment — a double expense.

“This is a cost that either the telecom operators have to cover by themselves or the state [has to defray],” said Karol Okonski, Poland’s minister of digital affairs, in an interview Wednesday. In Poland, Huawei is present in the core and the radio networks. So are the two other major vendors, Finland’s Nokia and Sweden’s Ericsson.

Poland, he said, is still weighing its 5G policy and hopes to have guidelines prepared by the end of June.

“It’s highly unlikely that we would ban Huawei completely from the Polish market,” he said. “But at the same time it’s hard to say whether we will be able to make our telecommunications infrastructure secure without intervention. The best scenario would be to come up with security rules that would allow us not to ban anyone but still feel that in the end our networks will be secure.”

He added: “We might have to have some limited ban on some of the vendors, otherwise we’ll feel it impossible to secure our networks in a way that we and our allies expect.”

U.S. security officials have been quietly preparing for all contingencies, including the prospect of other countries allowing Huawei equipment in their systems.

Last month, Sue Gordon, the deputy to the Director of National Intelligence, told an audience at the University of Texas, Austin, “we are going to have to figure out a way in a 5G world that we’re able to manage the risks in a diverse network that includes technology that we can’t trust.”

Officials have not let up at all on their efforts to persuade partners that Huawei’s presence poses a risk. But, Gordon said, “you have to presume a dirty network."

Industry officials and analysts said it is difficult without seeing details of the British restrictions to assess their impact on cyber and national security.

Even though Huawei will be barred from the network core, the radio antennas will contain more sensitive information than before hosted in the cloud, experts said. “There is a lot more automated response, threat detection and mitigation happening in the edge, which also could introduce vulnerabilities,” said one 5G industry official whose firm had not authorized him to speak on the record.

“It’s true that if you want to do the worst things—like disrupt a network—you probably have to get to the routers,” the industry official said. “But that does not mean you cannot cause very serious problems through the radio networks. It’s just harder to do. But not impossible at all.”

Earlier this month, in remarks in Washington, NSA Director Paul Nakasone said the concern with Huawei is it being headquartered in a nation “that doesn’t have respect for the rule of law, that doesn’t have a series of norms, that has a very, very concerted effort to partner both their government and their private sector together to make sure that the government’s will is being done.”

He added: “It’s not the fact that we have a smoking gun that we can’t identify. We have a loaded gun when you think about an adversary that has the ability to control your infrastructure.”