Huawei Technologies, the Chinese company put on a US blacklist because of national security concerns, secretly helped North Korea to build and maintain its commercial wireless network, a report claimed on Monday.
The Chinese telecommunications giant worked with state-owned Chinese company Panda International Information Technology on projects in North Korea over at least eight years, The Washington Post reported.
Sources said the US Commerce Department has been investigating Huawei since 2016 and is reviewing whether the company breached export control rules on sanctions for North Korea.
That would raise questions of whether Huawei, which has used US technology in its parts, breached American export controls to provide North Korea with equipment.
US Senators Chris Van Hollen and Tom Cotton said that the “revelation underscores its ties to North Korea and its serial violations of US law".
They said a defence reauthorisation bill under consideration in Congress contained new “provisions to better enforce sanctions on Pyongyang by making it clear that any company that does business with North Korea will face American sanctions".
The US put Huawei on a blacklist in May, banning US companies from selling most parts to Huawei without special licences.
But President Donald Trump said last month that American firms could resume sales in a bid to restart trade talks with Beijing.
Huawei did not immediately respond to a request for comment, but told the Post it had "no business presence" in North Korea.
Huawei and Panda left their Pyongyang office in the first half of 2016.