The use of robotics and similar technology has added a new dimension to the battlefield for all fighting forces, but the U.S. military in particular.

Fixed-wing unmanned aerial vehicles, first used in intelligence, surveillance and reconnaissance roles, drop ordnance on enemy targets; unmanned helicopters deliver supplies to the battlefield; and robots with sophisticated sensors discover and disable land mines.

The U.S. military this week announced the demonstration and testing of a new system that would benefit the infantryman who, out of necessity, may have to lug as much as a 100 pounds of equipment and supplies on his back.

It's known as the semi-autonomous Legged Squad Support System -- LS3. In essence, it's a robotic pack mule that will carry 400 pounds of equipment, traverse 20 miles at a time and act as an auxiliary power source for troops to recharge batteries for radios and handheld devices while on patrol.

"It's about solving a real military problem: the incredible load of equipment our soldiers and Marines carry in Afghanistan today," said Army Lt. Col. Joseph K. Hitt, program manager in the tactical technology office of the U.S. Defense Advanced Research Projects Agency.

DARPA noted as the amount and weight of equipment carried increases, so do incidents of fatigue, physical strain and degraded performance.

In 2009, DARPA began a five-year, $54 million project to develop the robot, which must become familiar with different types of terrain and with varying weather conditions, such as rain and snow.

A prototype of the system completed its first outdoor assessment in January and showed its ability to climb and descend hills as well as its perception capabilities.

More testing and demonstrations took place and now the robotic mule's sensors give it the capability to navigate around obstacles in darkness, maneuver in urban settings, respond to voice commands and gauge distances and directions.

Hitt said the device it can distinguish different forms of vegetation and has the capability to avoid obstacles such as rocks and logs.

New trials that will further develop its capabilities -- such as operating in desert terrain will soon begin.

"The vision is a trained animal and its handler," Hitt said. A squad leader, for example, would learn 10 basic commands to direct the machine.

"The technology of the robot focuses on mobility, perception and human-robot interaction," he said.

DARPA plans to deliver the first LS3 to a U.S. Marine Corps squad in two years.

"We have to make sure the robot is smart like a trained animal," he said. "We need to make sure it can follow a leader in his path, or follow in its own chosen path that's best for itself.

"The interaction between the leader and the robot [must be] intuitive and natural."