U.S. officials tracked workers from Chinese telecom companies Huawei Technologies and ZTE entering and exiting suspected Chinese spy facilities in Cuba, according to people familiar with the matter.

Intelligence reviewed during the Trump administration contributed to suspicions at the time that the companies might be playing a role in expanding China’s ability to spy on the U.S. from the island, according to the people. It couldn’t be learned whether the Biden administration has pursued that line of inquiry.

While neither Huawei nor ZTE is known to make the sophisticated tools governments would use for eavesdropping, both specialize in the technology needed to facilitate such an operation, such as servers and network equipment that could be used to transmit data to China, the people familiar with the matter said.

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In a statement, Huawei said it denied "such groundless accusations," adding that it was "committed to full compliance with the applicable laws and regulations where we operate."

A ZTE statement called The Wall Street Journal reporting "baseless."

China has maintained a spy base in Cuba since at least 2019, when Donald Trump was president, and the two countries already jointly run four eavesdropping stations on the island, according to U.S. officials. In addition, Beijing and Havana are negotiating to establish a new joint military training facility on Cuba’s northern coast, the Journal has reported. 

Beijing’s efforts to expand its intelligence gathering from Cuba are continuing, the White House has said. Following a 2019 upgrade to its intelligence-collection facilities on the island, Beijing "will keep trying to enhance its presence in Cuba, and we will keep working to disrupt it," a White House official said Monday.

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U.S. officials have long said China’s government might use the nation’s telecom companies to spy. The U.S. has been engaged in a yearslong campaign to persuade allies to shut Huawei in particular out of their next-generation telecommunications networks. Huawei has said it wouldn’t spy for China.

The Chinese Foreign Ministry has denied that China is spying in Cuba. A representative from the Chinese Embassy in Washington referred to China’s previous comments on Cuba. The Cuban Embassy in Washington didn’t respond to a request for comment, but has called the Journal’s earlier report on a Chinese spy station on the island "totally mendacious and unfounded." 

The U.S. Office of the Director of National Intelligence didn’t respond to requests for comment.

On Tuesday, Secretary of State Antony Blinken said he had told his counterparts in Beijing that the U.S. had "deep concerns" about Chinese spying and military activities in Cuba. 

"This is something we’re going to be monitoring very, very closely, and we’ve been very clear about that," he told reporters. "And we will protect our homeland; we will protect our interests."

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The White House didn’t respond to a request for comment on Huawei’s and ZTE’s potential roles in China’s spying operation in Cuba. National Security Council spokesman John Kirby said Tuesday it was "no secret or surprise that the PRC has been trying to improve their influence, their reach, and their intelligence collection capabilities in the Western Hemisphere and that includes the relationship that they had had for quite some time with Cuba."

"It’s not like we aren’t aware of it, it’s not like we haven’t been monitoring it," he said. "And quite frankly, it’s not like we haven’t taken steps and we’ll continue to take steps to thwart it and to be able to protect our own secrets and our own national security, and that’s the case in this space as well."

Rep. Mike Gallagher (R., Wis.), chairman of the bipartisan Select Committee on the Chinese Communist Party, on Tuesday sent a letter to Director of National Intelligence Avril Haines and Commerce Department Secretary Gina Raimondo seeking clarity on U.S. policies to control the export of U.S. technology to Chinese telecom companies.

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In the letter, which was viewed by the Journal, he said that Huawei has assisted the Cuban government in modernizing its telecommunications and internet infrastructure since the 2000s and that the company, along with ZTE and Great Dragon Information Technology Group, maintains a regular business presence on the island. 

Great Dragon couldn’t be reached for comment.

Gallagher wrote that because of China’s official policy of using Chinese commercial entities to build up its military, any enhancement of China’s intelligence capabilities in Cuba "is likely" to be aided by Chinese telecommunications companies. 

He speculated that these companies’ existing business operations in Cuba could provide cover for Chinese intelligence officials to travel to and from the island without creating the same suspicion as official travel.

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Gallagher posed a series of questions to the officials regarding the intelligence community’s awareness of the connections between Chinese signals-intelligence operations and commercial activities in Cuba and whether the information has been used to inform ongoing export-licensing decisions.

In 2019, the U.S. Commerce Department added Huawei to a so-called entity list requiring companies to get licenses to ship many goods to Huawei. In 2020, officials significantly expanded the licensing requirements. But the Commerce Department has issued many such licenses, enabling exporters to continue selling large amounts of tech to Huawei.

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The chair of the House Foreign Affairs Committee, Rep. Michael McCaul (R., Texas), has been spearheading an effort to pressure the Commerce Department to change its policy. In 2021, he released data showing the department had granted 113 export licenses enabling companies to sell about $61 billion of goods to Huawei from Nov. 9, 2020, through April 20, 2021.

The Commerce Department had restricted exports to ZTE on and off since 2016 until Trump said in 2018 that he would allow the company to resume buying U.S. goods in exchange for a fine of $1.3 billion and a leadership shake-up. 

Alan Estevez, the Commerce Department’s undersecretary for industry and security, has told lawmakers that his team is reviewing its policies and doing everything possible to prevent sensitive U.S. technology from getting into the hands of adversaries.

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A Commerce Department spokesman said Huawei still faces "significant export restrictions" and noted that the agency in April imposed the largest stand-alone civil penalty in its history against a U.S. company for selling hard-disk drives to Huawei without a license.

The spokesman added that ZTE remains subject to a settlement agreement with the Commerce Department that subjects it to additional oversight.

William Mauldin, Vivian Salama and Liyan Qi contributed to this article.