***Article first published by 'The Wall Street Journal' on April 24, 2019***

The U.K. government has agreed to allow Huawei Technologies Co. to build part of the country’s 5G telecom system—despite U.S. pressure on allies to exclude the Chinese telecom giant—but it will only be allowed to construct noncore parts of the network, according to an official familiar with the matter.

The decision is a victory for Huawei in its fight against a U.S. campaign to block the use of its 5G equipment in the networks of U.S. allies. The U.S. has long held that Huawei equipment is a security threat, which the telecommunications company forcefully denies.

The decision came at a meeting of Britain’s National Security Council on Tuesday attended by Prime Minister Theresa May and several British government ministers.

They agreed that Huawei should be allowed to participate in the construction of the network, but would be barred from involvement in its critical core, the official said. The decision wouldn’t be final until announced before lawmakers in the House of Commons.

In a written statement, the company said it “welcomes reports that the U.K. government is moving toward allowing Huawei to help build the U.K.’s 5G network.”

A government spokesman wouldn’t confirm the decision, saying National Security Council discussions are confidential, but said an announcement would come in due course.

He said the security and resilience of the U.K.’s telecom networks were of paramount importance. The government had “conducted an evidence-based review of the supply chain to ensure a diverse and secure supply base, now and into the future,” he said.

The U.S. effort has been met with mixed success so far. Australia has indicated it won’t use Huawei gear in its 5G networks, while the New Zealand government has blocked a bid by one carrier to do so. Germany has said it sees no reason to block Huawei, despite a U.S. pledge to limit intelligence-sharing with Berlin if it does so.

The stakes for Huawei, however, are arguably highest in the U.K. because no other Western country subjects its products to such scrutiny. The country is one of the company’s oldest markets outside China, and a Huawei-run lab near Oxford that is overseen by U.K. officials pores over the company’s products for security flaws as a condition of its participation in the market.

Last month, the U.K. accused Huawei of failing to repeatedly address security issues, a significant setback for the Chinese company.

The U.K. decision doesn’t give Huawei a full pass: It will continue to exclude the company’s equipment from the network core. That includes centralized parts of the network such as data centers, which perform critical functions like access control, voice and data routing.

Noncore parts of the network include more peripheral equipment such as base stations that connect the core to consumers’ devices.

Huawei is the world’s largest supplier of telecom equipment and a leader in 5G technology and patents. Last week, John Suffolk, Huawei’s global security and privacy officer and the U.K.’s former top information-security official, criticized the U.S. campaign against Huawei and said efforts to blacklist the company will only hurt consumers.

“If you’re saying, ‘I want to take out the world leader,’ then I think you’re doing your citizens a disservice,” he said at an event at the telecom company’s Shenzhen headquarters. “No evidence has ever been presented that Huawei has ever done something wrong.”

The company has continued to post strong financial results despite U.S. pressure. It said Monday its first-quarter revenue rose 39% to nearly $27 billion, and it has signed more than 40 commercial 5G contracts with operators around the world.

Write to Max Colchester at max.colchester@wsj.com and Dan Strumpf at daniel.strumpf@wsj.com