It sounded like something pulled straight from a grisly scene in Terminator: an unstoppable military robot that powered itself by devouring everything in its path - including trees, grass and even, according to reports, dead bodies.

But after a string of headlines that labelled the machine a "corpse eater" and "creepy", the robot's creators have gone on a PR offensive to extinguish the rumour that their invention will feed on human or animal flesh.

The machine's inventors say that the Energetically Autonomous Tactical Robot – known as Eatr for short – does indeed power its "biomass engine" by digesting organic material, but that it is not intended to chomp its way through battlefields of fallen soldiers.

"We completely understand the public's concern about futuristic robots feeding on the human population, but that is not our mission," said Harry Schoell, the chief executive of Cyclone Power Technologies, one of the companies behind the machine.

"We are focused on demonstrating that our engines can create usable, green power from plentiful, renewable plant matter. The commercial applications alone for this earth-friendly energy solution are enormous."

The remarkable move is in reaction to the buzz the project created when it emerged that it was already in the testing phase, thanks to funding from the Pentagon.

The concept was originally put forward in 2003, and has been pushed forward with money from the US military's Defence Advanced Research Projects Agency, Darpa, a successor to the organisation that funded early development of the internet.

US officials hope that the steam-powered engine can be used by the military to create a self-sufficient robot that could survive on its own for months at a time. Possible uses put forward by the team include a battlefield ambulance or mobile gun turret.

The early version of Eatr runs on twigs, wood chips and other plant based material, fed into an engine that burns the material and uses it to propel itself around.

Another of the robot's inventors, Dr Robert Finkelstein of Robotic Technology Inc (RTI), said that Eatr had built-in systems that would help it determine whether material that it ingested was animal, vegetable or mineral.

"If it's not on the menu, it's not going to eat it," he told Fox News. "There are certain signatures form different kinds of materials that would distinguish vegetative biomass from other material."

It can also use more conventional fuels, such as petrol, diesel or cooking oil, to keep going. But in a statement put out by the group, it reiterated that it would be illegal to create a robot that used dead bodies as an energy source.

"Descration of the dead is a war crime under Article 15 of the Geneva Conventions, and it is certainly not something sanctioned by Darpa, Cyclone or RTI."