Robotic systems and unmanned vehicles are playing an ever-growing role in the US military - but don't expect to see Terminator-style droids striding across the battlefield just yet.

A top Pentagon official on Wednesday gave a tantalizing peek into several projects that not long ago were the stuff of science fiction, including missile-dodging satellites, self-flying F-16 fighters and robot naval fleets.

Though the Pentagon is not planning to build devices that can kill without human input, Deputy Secretary of Defense Robert Work hinted that could change if enemies with fewer qualms create such machines.