Tesla’s Elon Musk, Google’s Mustafa Suleyman and over 100 of the world’s experts in robotics and artificial intelligence have signed an open letter demanding that the development and use of killer robots be banned.

116 people working in the field, all from 26 countries, are a part of the campaign to outlaw autonomous weapons, as the Guardian reports. The open letter was prompted by the UN’s recent vote to begin discussions on weapons like tanks, automated machine guns and drones. They detail that instigating an “arms race” for AI-powered weapons would spark the “third revolution in warfare”.

“Once developed, lethal autonomous weapons will permit armed conflict to be fought at a scale greater than ever, and at timescales faster than humans can comprehend,” the letter reads. “These can be weapons of terror, weapons that despots and terrorists use against innocent populations, and weapons hacked to behave in undesirable ways.”

“We do not have long to act. Once this Pandora’s Box is opened, it will be hard to close.”

The group of experts are asking that “morally wrong” lethal robotics and weapons be added to the UN’s list under the convention of certain conventional weapons. The list includes blinding lasers and chemicals.

The letter was released at the International Joint Conference on Artificial Intelligence in Melbourne, Australia. A similar campaign was launched two years ago at the same event, backed by Musk and Stephen Hawking, calling for a ban on deadly robotics.

There’s a fear that autonomous weapons would result in a larger loss of human life, eradicating the battlefield to spread AI militia elsewhere. Experts say this could be possible in just a few years, as technology develops. This letter calls for urgent action, as the UN moves forward with reviewing autonomous weaponry.

Elon Musk has been very vocal in his distrust of such AI and robotics. He recently described AI as humanity’s “biggest existential threat”, and engaged in a war of words with Mark Zuckerberg.

As the Guardian details, there are already some autonomous killing machines in use. We’re not talking Terminator vibes – a Samsung SGR-A1 sentry gun is used on the South Korean border. It’s said to be capable of firing autonomously, uses voice recognition, surveillance, tracking and can fire from a machine gun or launch grenades. There’s also the Taranis drone in the UK, which is in development. Russia is said to be working on an unmanned combat ground vehicle, while the U.S and other countries continue developing both remote controlled and autonomous robotic tanks.