The by the U.S. House of Representatives' Permanent Select Committee on Intelligence said the possibility of ties between the two companies and the Chinese government of China using their gear to conduct electronic espionage. It advised U.S. companies not to buy equipment from the two companies. Huawei and ZTE have the report's conclusions.

The committee said it compiled the report after Huawei requested such a study last year. The company sought to defend itself against allegations that it was partly owned or influenced by the Chinese government. Huawei and ZTE both have been targets of U.S. government pressure in the past, leading to Huawei's for a small security software company last year and regulators a purchase of 3Com by Huawei and Bain Capital in 2008.

Partly because of that opposition, Huawei and ZTE have not made significant inroads into the biggest U.S. carrier networks despite being major competitors in much of the rest of the world. But the report named several customers that have bought at least some equipment from Huawei. On Tuesday, three of those companies defended their choices, saying they took steps to make sure their networks were secure.

Clearwire, which runs the national WiMax network used by Sprint Nextel and is now working on an LTE system, said it buys some of the radios for the edge of its WiMax network from Huawei. The Chinese company is just one of four vendors supplying those radios, alongside Samsung Electronics and Nokia Siemens, Clearwire said in a statement.

The edge radios aren't directly connected to the core network systems that manage and process traffic on the network, Clearwire said. But the carrier takes security precautions in any case.