The US government's crackdown on Chinese smartphone makers Huawei and ZTE is intensifying.

The Pentagon has banned the sale of Huawei and ZTE phones in retail stores on US military bases, citing security concerns, The Wall Street Journal reports.

"Huawei and ZTE devices may pose an unacceptable risk to the department's personnel, information and mission," Army Maj. Dave Eastburn, a Pentagon spokesman, told the Journal. "In light of this information, it was not prudent for the department's exchanges to continue selling them."

Members of the military can still buy Huawei and ZTE phones elsewhere, if they so choose, but Eastburn warned them to "be mindful of the security risks," the report notes. Unnamed sources told the newspaper that the Pentagon is worried the devices will allow the Chinese government to track soldiers' locations.

The move comes after the US Commerce Department last month banned US companies from selling components to ZTE for seven years. Meanwhile, that same month, the Federal Communications Commission unanimously approved a measure that would eliminate a government subsidy for any US telecom carrier that buys from Huawei or ZTE; a second vote will make it official.

Best Buy in March reportedly cut ties with Huawei, following the lead of US carriers like AT&T and Verizon, which decided not to sell the company's Mate 10 Pro due to pressure from the US government.

The campaign against Huawei and ZTE dates back to 2012 when the House Intelligence Committee issued a report warning that the firms might be using their entrance into the U.S. market as a way to spy for the Chinese government – allegations Huawei and ZTE have both rejected.

This article originally appeared on PCMag.com.