A pre-emptive ban is needed to halt the production of weapons capable of attacking targets without any human intervention, a new campaign has urged.
Jody Williams, from the Campaign to Stop Killer Robots, told the BBC such weapons, which do not yet exist, would be regarded as "repulsive".
But some scientists argue existing laws are sufficient to regulate their use, should they become a reality.
The UK government has said it has no plans to develop such technology.
Weapons with a degree of autonomy, including Unmanned Aerial Vehicles - commonly known as drones - are already widely used on the battlefield.
Such weapons are described as "human-in-the-loop" systems because they can only select targets and deliver lethal force with a human command.
But organisers of the Campaign to Stop Killer Robots - a global effort being launched on Tuesday - say advances in robotic technology mean it is only a matter of time before fully autonomous "human-out-of-the-loop" systems - capable of firing on their own - are developed.
They argue that giving machines the power over who lives and dies in war would be an unacceptable application of technology, and would pose a fundamental challenge to international human rights and humanitarian laws.
Estimates vary over how long it could be before such weapons are available, but the group says a new treaty is needed to pre-emptively outlaw their development, production and use.
Campaign leader Ms Williams, who won a Nobel Peace Prize in 1997 for her work in bringing about a ban on anti-personnel landmines, told BBC News: "As people learn about our campaign, they will flock to it.
"The public conscience is horrified to learn about this possible advance in weapons systems. People don't want killer robots out there.
"Normal human beings find it repulsive."
But some experts have questioned the need for a ban, arguing instead for an open debate about the legal and ethical implications of such weapons.
Roboticist Professor Ronald Arkin, from the Georgia Institute of Technology in the US, told the BBC: "The most important thing from my point of view is that we do not rush these systems into the battlefield.
"A moratorium as opposed to ban - where we say, 'we're not going to do this until we can do it right' - makes far more sense to me than simply crying out, 'ban the killer robots'.
"Why should we do that now?"
Recent statements by UK and US governments suggest a reluctance to take human beings fully "out-of-the-loop" in warfare.
In March, Lord Astor of Hever - the UK's parliamentary under secretary of state for defence - said the Ministry of Defence "currently has no intention of developing systems that operate without human intervention".
And a directive issued by the US Department of Defense in November 2012 stated that all weapons with a degree of autonomy "shall be designed to allow commanders and operators to exercise appropriate levels of human judgment over the use of force".