Elon Musk and Stephen Hawking, along with hundreds of artificial intelligence researchers and experts, are calling for a worldwide ban on so-called autonomous weapons, warning that they could set off a revolution in weaponry comparable to gunpowder and nuclear arms.

In a letter unveiled as researchers gathered at the International Joint Conference on Artificial Intelligence in Buenos Aires on Monday, the signatories argued that the deployment of robots capable of killing while untethered to human operators is “feasible within years, not decades.” If development is not cut off, it is only a matter of time before the weapons end up in the hands of terrorists and warlords, they said.

Unlike drones, which require a person to remotely pilot the craft and make targeting decisions, the autonomous weapons would search for and engage targets on their own. Unlike nuclear weapons, they could be made with raw materials that all significant military powers could afford and obtain, making them easier to mass-produce, the authors argued.

Image A scene from the science fiction fantasy “Terminator Genisys.” Experts warned that autonomous weapons could be “feasible within years, not decades.” Credit... Paramount Pictures

The weapons could reduce military casualties by keeping human soldiers off battlefields, but they could also lower the threshold for going to battle, the letter said. “If any major military power pushes ahead with A.I. weapon development, a global arms race is virtually inevitable, and the endpoint of this technological trajectory is obvious: autonomous weapons will become the Kalashnikovs of tomorrow,” it said.