Defense Secretary Pete Hegseth has signed off testing for a military-grade heat ray to potentially be used at the U.S.-Mexico border – a measure other U.S. officials have previously passed on.

The Pentagon gave the Department of Homeland Security permission to test and develop potential tactics for the heat ray to be deployed at the southern border, according to a memo obtained by CNN.

The non-lethal weapon - officially known as the Active Denial System - sends an invisible beam of energy shooting out to a distance of around half a mile. The energy beam causes an intense burning sensation on human skin and is meant to act as a deterrent, the U.S. military said in the memo.

Hegseth signed and approved a seven-month loan for the weapon starting in September.…