Robots will be armies of the future in a case of science fact catching up to fiction, a researcher told an elite TED gathering on Wednesday.

Peter Singer, who has authored books on the military, warned that while using robots for battle saves lives of military personnel, the move has the potential to exacerbate warfare by having heartless machines do the dirty work.

"We are at a point of revolution in war, like the invention of the atomic bomb," Singer said.

"What does it mean to go to war with US soldiers whose hardware is made in China and whose software is made in India?"

Singer predicts that US military units will be half machine, half human by 2015.

The US Army already recruits soldiers using a custom war videogame, and some real-world weapon controls copy designs of controllers for popular videogame consoles.

Attack drones and bomb-handling robots are already common in battle zones.

Robots not only have no compassion or mercy, they insulate living soldiers from horrors that humans might be moved to avoid.

"The United States is ahead in military robots, but in technology there is no such thing as a permanent advantage," Singer said. "You have Russia, China, Pakistan and Iran working on military robots."

There is a "disturbing" cross between robotics and terrorism, according to Singer, who told of a website that lets visitors detonate improvised explosive devices from home computers.

"You don't have to convince robots they are going to get 72 virgins when they die to get them to blow themselves up," Singer said.

Robots also record everything they see with built-in cameras, generating digital video that routinely gets posted online at YouTube in graphic clips that soldiers refer to as "war porn," according to Singer.

"It turns war into entertainment, sometimes set to music," Singer said. "The ability to watch more but experience less."

Robotics designer David Hanson offered hope when it comes to making robots a little more human.

Hanson builds robots that have synthetic flesh faces and read people's expressions in order to copy expressions.

"The goal here is not just to achieve sentience, but empathy," Hanson said.

"As machines are more capable of killing, implanting empathy could be the seeds of hope for our future."

Hanson demonstrated a lifelike robotic bust of late genius Albert Einstein that makes eye contact and mimics people's expressions.

"I smiled at that thing and jumped out of my skin when it smiled back," TED curator Chris Anderson quipped. "It's freaky."