Image copyright 2009 Warner Bros. Courtesy of Industrial Light & Magic

Be afraid. Be very afraid of these three letters: LAR.

Lethal autonomous robots is what Christof Heyns, United Nations special rapporteur on extrajudicial, summary, or arbitrary executions, wants you to think about. He wants a global ban on the development of machines that can target people and kill them without supervision.

"The possible introduction of LARs raises far-reaching concerns about the protection of life during war and peace," Heyns said Thursday during the presentation of his latest report to the U.N. Human Rights Council. "If this is done, machines and not humans will take the decision on who is alive or dies."

Heyns, a professor of human-rights law at the University of Pretoria in South Africa, wants the council to consider adopting a moratorium on LARs until the international community reaches consensus on the issue. He called for "serious and meaningful international engagement on this issue before we proceed to a world where machines are given the power to kill humans."

"War without reflection is mechanical slaughter," he said in a release. "In the same way that the taking of any human life deserves as a minimum some deliberation, a decision to allow machines to be deployed to kill human beings deserves a collective pause worldwide."

Heyns said LARs could make it easier for countries to go to war, and could lack the ability to comply with international human rights law. Apart from that, they would be acting in a grey area of legal accountability.

Heyns' call comes only a month after Human Rights Watch launched its global Campaign to Stop Killer Robots. The NGO also fears a looming robot arms race.

While global military forces have deployed lethal drones that require humans to be in the loop, LARs are seen by some as an inevitable evolution.

"Although humans today remain more capable than machines for many tasks," a U.S. Air Force report says, "by 2030 machine capabilities will have increased to the point that humans will have become the weakest component in a wide array of systems and processes."

Hear more comments by Heyns in the clip below.