GENEVA » Nations should agree to a moratorium on developing robots for war that can function autonomously before it is too late to stop their use, a U.N. human rights expert warned today.

U.N. special rapporteur Christof Heyns urged a temporary freeze on producing or using so-called killer robots, saying it would give nations time to think through the implications of creating them while “the genie is still in the bottle” technologically.

Programming machines to kill without humans making decisions could encourage more wars and make it more difficult to hold anyone accountable for war crimes, he told reporters in Geneva.

“Time is of the essence,” he said of the need to decide now on how to use the robots, before they become a practical reality. “Trying to stop technology is a bit like trying to stop time itself — it moves on.”

Heyns said the technology is quickly emerging and nearly available now that could lend machines the power to autonomously kill humans after “the turn of a switch,” but lack the ability to make fine distinctions according to international humanitarian law. “We are pretty close,” he said.

In a report to the U.N. Human Rights Council, Heyns urged nations “to declare and implement national moratoria on the production, assembly, transfer, acquisition, deployment and use” of the robots to give time to develop a global framework for their use.

Another big danger of developing these kinds of robots, he said, is that it will make it easier for nations to go to war because of the increasing detachment between people and the decision to kill.