WASHINGTON -- Two China-based telecommunications companies on Thursday categorically repudiated 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.

"It would be immensely foolish for Huawei to risk involvement in national security or economic espionage," senior vice president Charles Ding of Huawei said at the session, which marked the first time for a Chinese company to participate in a US Congress hearing.

Among the allegations are that the two firms have special relations with the Chinese government and that they designedly place backdoors in their products that could be used to make foreign espionage easier.

"There are no backdoors in any of Huawei's equipment," Ding stressed, noting that the so-called backdoors might refer to software bugs that are unavoidable in the industry.

"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 said.

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? Let me answer emphatically: No!" he told the panel.

Speaking to Xinhua, Zhu said that, as a globally operating company, ZTE also has its own trade secrets and intellectual property rights to protect.

The panel is expected to release a classified and an unclassified report on the investigation in the first or second week of October.