Updated

U.S. lawmakers and intelligence officials are expressing concern about the threat of Chinese telecommunication companies operating inside the country.

This week, the Senate Intelligence Committee held a hearing on global terror threats attended by the directors of the CIA, the FBI and the National Security Agency.

Tom Cotton, the junior U.S. Senator from Arkansas, asked some of the most pointed questions to the panel of U.S. intelligence officials during the hearing that took place earlier this week.

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Cotton prefaced his questions by stating that there is a “threat posed by China and specifically Chinese telecomm companies."

The Senator added he had introduced legislation, along with other senators, which says that “the U.S. government can’t use Huawei or ZTE and the U.S. government can’t use companies that use them.”

Cotton then addressed his questions to FBI director Christopher Wray and NSA director Adm. Mike Rogers.

"We're deeply concerned about the risks of allowing any company or entity that is beholden to foreign governments that don't share our values to gain positions of power inside our telecommunications networks," Wray said in response.

He added that entities with the capacity “to exert pressure or control over our telecommunications infrastructure” or “maliciously modify or steal information” and “conduct undetected espionage...Those are the kinds of things that worry us.”

When Cotton turned his questions to Mike Rogers, the NSA director said that, "You need to look long and hard at companies like this.”

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U.S. telecom companies drop plans to offer phones

U.S. telecom companies have responded to requests, according to Wray.

“We’ve been gratified to date by the response of large U.S. telecommunications providers to our trying to raise awareness on this issue,” he said.

Both Verizon and AT&T have dropped plans to offer phones from Huwaei, according to various media reports.

Neither Verizon nor AT&T has responded yet to a request for comment from Fox News.

Huawei was ranked just behind market leaders Apple and Samsung in global smartphone shipments in the fourth quarter of 2017, according to market researcher IHS Markit. ZTE was also ranked in the top ten.

Huawei's international strategy "hit a roadblock in the U.S, as government opposition is closing the path to carrier partnerships for its flagship devices," IHS Markit said in a statement.

“The [U.S. government] has been concerned about Huawei for many years,” James Lewis, Senior Vice President, Center for Strategic and International Studies, told Fox News.

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“The Chinese had an early focus on telecom as a strategic industry because of the intelligence advantages it confers," he added.

"ZTE is proud of the innovation and security of our products in the US market," a ZTE spokesperson told Fox News. "As a publicly traded company, we are committed to adhering to all applicable laws and regulations of the United States, work with carriers to pass strict testing protocols, and adhere to the highest business standards."

The spokesperson added: "Our mobile phones and other devices incorporate US-made chipsets, US-made operating systems, and other components. ZTE takes cybersecurity and privacy seriously and remains a trusted partner to our US suppliers, US customers and the people who use our high quality and affordable products for their communications needs." 

Huawei has yet to respond to a request for comment.

This story has been updated to include ZTE's comments.