The two companies rejected fears that their expansion into the US was a security risk and said they operated independently from the Chinese government.
The committee’s report could be followed by proposals to exclude Huawei and ZTE products from the US market, if it is determined that they pose a security threat.
"We have heard reports about backdoors or unexplained beaconing from the equipment sold by both companies," said Committee Chairman Mike Rogers in his opening statement, according to Reuters.
Huawei is represented at the hearing by SVP Charles Ding, who said in written testimony the company “will not jeopardise our global commercial success nor the integrity of our customers' networks for any third party, government or otherwise."
Both he and Zhu Jinyun, SVP for North America and Europe at ZTE, denied under oath that their companies had installed back-door access into their equipment and vowed that they would never bow to requests from the Chinese government to exploit their products for espionage. The two also agreed to send lists of their Chinese communist party committee members.
The investigation is expected to be completed by the first week of October.
Huawei and ZTE have struggled to make any ground in the US market, due to concerns over their ties with the Chinese government.
The country’s stance towards the vendors contrasts starkly to that of the UK, where this week Huawei announced a $2 billion investment plan.
Australia has taken a similar stance to the US and banned Huawei from taking part in its $38 billion National Broadband Network (NBN) project in March.
Today Huawei reportedly urged the country’s government to not discriminate against foreign communication companies.
