Two China-based telecommunications companies repudiated Thursday allegations that they deliberately leave backdoors in their products to assist foreign espionage on US security and commercial secrets.

Huawei and ZTE defended their integrity at a hearing held by a US House panel to examine whether the two telecom equipment makers pose any threat to US national security.

This was the first time for Chinese companies to participate in a US Congress hearing.

"We launched this investigation to determine whether allowing Chinese companies increased access to our US telecommunications market places us at risk for greater foreign espionage, theft of US trade secrets and increased vulnerabilities to our critical infrastructure," Dutch Ruppersberger, ranking member of the House Permanent Select Committee on Intelligence, said in the opening statement.

"Huawei and ZTE have become dominant global players in the telecommunications market, leaving the world increasingly dependent on their telecommunications goods and services," said Mike Rogers, chairman of the committee.

"We have heard reports about backdoors or unexplained beaconing from the equipment sold by both companies," he said.

In reply, Huawei's Senior Vice President Charles Ding said that he wants to "set the record straight about Huawei."

"Business is business...It would be immensely foolish for Huawei to risk involvement in national security or economic espionage," said Ding.

"Huawei has not and will not jeopardize our global commercial success nor the integrity of our customers' networks for any third party, government or otherwise," he noted.

Ding said, "Our customers throughout the world trust Huawei," which operates in more than 140 countries and about 70 percent of its revenue comes from overseas market.

ZTE's senior vice president for North America and Europe, Zhu Jinyun, also firmly rejected the charges.

"Would ZTE grant China's government access to ZTE telecom infrastructure equipment for a cyber attack?" said Zhu at the hearing, "Let me answer emphatically: no!"

Zhu told Xinhua that as a globally operating company, ZTE also has its own trade secret and intellectual property rights (IPR) to protect.

The two Chinese executives also faced questions from other lawmakers as to whether they got concessional funding from the Chinese government.

Ding said Huawei's success "has been built on entrepreneurship, innovation and dedication, not on favoritism from any government."

The firm is one of the major global telecom gear providers, second only to Sweden's Ericsson in sales. Meanwhile, it is the largest patent holder in China, employing 65,000 dedicated R&D engineers, the most in the industry.

Over the past decade, Huawei has invested more than $15 billion in R&D and has filed more than 50,000 patent applications, according to the Huawei's written testimony.

Zhu, for his part, noted that ZTE's success is just one snapshot of the overall prosperity in Shenzhen, one of the first group of China's special economic zones, nowadays China's high tech center, much like Silicon Valley.

ZTE was founded in 1985 with its founder Hou Weigui's vision to provide universal telecommunications service to China's undeveloped and rural areas, which was not something imposed or mandated by Beijing.

"ZTE is not an SOE (state-owned enterprise) or government controlled...ZTE is owned by over 140,000 public shareholders, including many of the world's leading institutional investors," said Zhu.

Earlier this year, Australia's federal government blocked Huawei from bidding for contracts on a huge broadband project, also known as National Broadband Network (NBN), due to fears of Chinese cyber attacks.

The move was criticized as "a huge insult" by New South Wales Premier Barry O' Farrell, who said the federal government lacked clarity and rationale when it came to critical foreign relations decisions.

In the United States, Huawei was also forced to back away from several expansion efforts amid pressure from Washington, according to a 78-page report released by Huawei on Sept. 4.

"During the past few years, unspecified allegations in the US have led to severe anti-market measures to block Huawei's expansion efforts," the report said.

"Much of the evidence fueling lawmakers' concerns remains classified," it said. "However, when one set of allegations are substantiated with another set of allegations, the line between investigation and maltreatment grows thin."

There would be a classified report and an unclassified one coming in the first or second week of October as a result of the investigation on whether there are backdoors from the equipment sold by both companies, said Rogers.

The ZTE executive also told the committee that Chinese companies should not be a focus of investigation to the exclusion of the much larger Western vendors.

"Virtually all of the telecom equipment now sold in the US and throughout the world contains components made, in whole or in part, in China," said Zhu.

When asked about a report that at least one ZTE device had a "backdoor," Zhu said this was incorrect and the report was "not fact-based."

"The so-called backdoors are actually software bugs that are unavoidable among the industry," Zhu said, adding that IT giants like Microsoft, Google and Apple all face the same problem.