The Pentagon’s No. 2 civilian official said Wednesday that the Defense Department is concerned that adversary nations could empower advanced weapons systems to act on their own, noting that while the United States will not give them the authority to kill autonomously, other countries might.

Deputy Defense Secretary Robert O. Work said the Pentagon hasn’t “fully figured out” the issue of autonomous machines, but continues to examine it. The U.S. military has built a force that relies heavily on the decision-making skills of its troops, but “authoritarian regimes” may find weapons that can act independently more attractive because doing so would consolidate the ability to take action among a handful of leaders, he said.

“We will not delegate lethal authority to a machine to make a decision,” Work said. “The only time we will… delegate a machine authority is in things that go faster than human reaction time, like cyber or electronic warfare.”