The XOS2 suit - pronounced "exos" - produced by US defence technology firm Raytheon Sarcos allows the user to carry 70kg with apparently little or no effort and punch through four planks of wood at once.

The exoskeleton has been designed with two applications in mind: firstly, the combat variant, which is a waist-down suit intended for use supporting heavy backpacks; and, secondly, the logistics version, which is a full suit intended to be used by personnel carrying water, supplies and ammunition boxes or tank shells.

Iron Man actor Clark Gregg, who plays Agent Phil Coulson in the films, was given the opportunity to try the suit at the firm's research lab in Salt Lake City, Utah, last week.

He said: "It's the closest thing we have at the moment to the Iron Man suit. That it's becoming real so quickly is remarkable."

The XOS2 is the second prototype of the model, which has been made more fuel efficient. The firm expect to release a version of the suit which is "tethered" first, which means it is attached to its power source permanently, before improvements are made to allow the wearer full independence of movement.

Dr Fraser Smith, the firm's vice-president of operations, said: "We would expect them to appear in theatre [war zones] probably in about five years for the tethered version and perhaps three to five after that for the untethered version."

In the Iron Man films, with Robert Downey Junior in the eponymous role based on the Marvel Comics character, a power suit allows the wearer virtually unlimited strength and the ability to fly.