'We have evidence that Huawei has the capability secretly to access sensitive and personal information in systems it maintains and sells around the world,' national security adviser Robert O'Brien told the Wall Street Journal. 

While all network hardware operators build in 'lawful intercept' interfaces that allow law enforcement to access mobile network information with a court order, it is typically impossible to do so without the knowledge and approval of the mobile carrier.

U.S. officials say that Huawei's back door allows the company to access network data without the carrier's knowledge, potentially giving the Chinese government a potent spy tool.

Huawei denies the allegations, telling the Journal that it 'has never and will never do anything that would compromise or endanger the security of networks and data of its clients.'