But the fund is not a line of credit to finance Huawei's own operations, and Huawei doesn't control who can use it, Plummer said. In addition, the arrangement hasn't given Huawei a significant edge over competitors in securing deals, because it has barely been used, he said. Since 2005, money from the fund has been used for 35 projects that Huawei was involved in, but only $4.2 billion in credit was extended and only $2.99 billion of that credit was actually used, according to Plummer.

Over the same period, Huawei did $110 billion worth of business around the world, he said.

Huawei does have a line of credit from the bank for its own use, but it is only worth $1.5 billion, a small part of the $25 billion in credit that Huawei has secured from 28 banks worldwide, Plummer said. Only 48 percent of that total figure comes from banks in China, he said.

Hochberg alleged that Huawei had an unfair advantage over U.S. vendors such as Cisco Systems and Patton Electronics, a small networking company in Gaithersburg, Maryland. Huawei and other non-U.S. companies use government help to offer below-market-rate financing to potential customers, beating out U.S. companies in the process, he said. Hochberg noted that the Ex-Im Bank has provided Patton a $4 million government-backed line of credit for working capital.

After Huawei challenged Hochberg's comments, the Ex-Im Bank didn't back down from the speech.