International experts are meeting to discuss ways to define and deal with "killer robots".
The week-long gathering is the second of its kind this year at UN offices in Geneva to focus on futuristic weapons systems that could conduct war without human intervention.
It aims to examine such lethal autonomous weapons systems and explore ways of regulating them.
In theory, fully autonomous, computer-controlled weapons do not exist yet, according to UN officials. The debate is still in its infancy, and the experts have at times grappled with basic definitions.
The United States has argued that it is premature to establish a definition of such systems, much less regulate them.
But top advocacy groups say governments and militaries should be prevented from developing such systems, which have sparked fears and led some critics to envisage harrowing scenarios about their use.
As the meeting opened, Amnesty International urged countries to work towards a ban.
Amnesty researcher on artificial intelligence Rasha Abdul Rahim said killer robots are "no longer the stuff of science fiction", warning that technological advances are outpacing international law.
Part of the trouble for campaigners, however, is that the UN-supported organisation works by consensus, meaning that any one country - like big military powers - could foil efforts to reach an international ban.
Amandeep Gill, a former Indian ambassador to the UN-backed Conference on Disarmament who is chairing the meeting, said progress is being made. He summarised three general camps of countries: one seeks a formal, legal ban on such weapons; another wants a political, but non-binding agreement; and a last one wants no changes at all.
"We are coming closer to an agreement on what should be the guiding principles - guiding the behaviour of states, and guiding the development and deployment of such systems around the world," Mr Gill told reporters. "And this is not an insignificant outcome."
