A redesigned version of Atlas - one of the world's most advanced robots - has been revealed by the Pentagon.
The android gains more advanced wrists, allowing it to turn door handles without having to move its entire arm.
But the key change is the inclusion of a battery pack, allowing it to function without an attached power cord.
The addition means the Google-owned machine qualifies for the final round of a robotics competition run by the US military's R&D unit, Darpa.
Seven of the 20 teams expected to take part in June's event intend to use Atlas. They will distinguish themselves by adding their own software to the machine and adopting different strategies to cope with the challenges posed.
The final event's rules state that the human-supervised robots taking part cannot be connected to power cords, fall arrestors, or wired communications.
"Being cordless is absolutely essential for operation in the field," robotics expert Prof Noel Sharkey told the BBC.
"A tethered robot would easily become snared and tangled anywhere but the simplest environment.
"It is crucial for full robot autonomy and it will greatly enhance the operational scope required by Darpa."
The latest version of Atlas is slightly taller and heavier than before, standing 6ft 2in (1.88m) high and weighing 156.4kg (345lb).
According to its manufacturer, Google's Boston Dynamics division, 75% of the humanoid machine is new - only its lower legs and feet remain unchanged.
The inclusion of a 3.7kWh lithium-ion battery is said to have the potential to last about one hour if the machine is carrying out "mixed tasks" including walking, climbing stairs and using tools.
However, a new, quieter variable-pressure pump system added to machine will run down the power pack more quickly if used at its maximum setting,
"The operator will be able to run the robot on a mid-pressure setting for most operations to save power, and then apply bursts of maximum pressure when additional force is needed," explained Gill Pratt, programme manager for the Darpa Robotics Challenge.
"The teams are going to have to game out the right balance of force and battery life to complete the course."
Other upgrades to Atlas include:
- Repositioned arms and shoulder to let the robot see its hands in motion, which should help its operators control it
- A wireless router in its head to provide a radio link to the teams
- Resized motors in its hips, knees and back to give them extra strength
Hole in the wall
Darpa's competition is designed to further development of robots that could be used to assist humans in disaster zones.
During the competition, operators will not be allowed to physically intervene if their robots fall over or otherwise get stuck.
Higher scores will be given for completing tasks more quickly, such as removing debris from a doorway, cutting a hole in a wall using a cordless drill and driving a utility vehicle.
A team from the Florida Institute for Human & Machine Cognition came second using an earlier version of Atlas in the previous round of the contest, held in December 2013.
The winner, however, was Schaft, a robot created by a spin-off from the University of Tokyo - which is also owned by Google.