Two astronauts completed a spacewalk on Sunday to install the arms of the $200-million Canadian-built Dextre robot built for the International Space Station.

dextre-cp-4522225

Dextre seen here in the final stages of installation. ((NASA/Associated Press))

Flight director Dana Weigel said the robot is looking more human-like as its assembly progresses.

"You can see arms and legs, and you can now see pretty much what Dextre is going to look like," Weigel said after the second spacewalk devoted to assembly work.

Spacewalkers Rick Linnehan and Mike Foreman spent seven hours and eight minutes assembling the gigantic robot overnight. The pair struggled to release one of the arms from the transport bed where it had been latched down for the launch of the space shuttle Endeavour last Tuesday.

Two of the bolts wouldn't budge, even when the astronauts banged on them and yanked as hard as they could. They finally succeeded by using a pry bar.

Dextre's two hands have built-in socket wrenches, cameras and lights. Once fully assembled and extended, the robot will stand 3.5 metres tall.

For nearly two days, a cable design flaw prevented NASA from getting power to Dextre to keep its joints and electronics from freezing to the point of sustaining damage. The space station's Canadarm2 grabbed hold of the robot late Friday to supply it with electricity.

Only one arm of Dextre is designed to move at a time to keep the robot stable and avoid a two-arm collision.

Space station astronauts will be able to control Dextre, as will flight controllers on the ground. The robot will be attached at times to the end of the space station mechanical arm. It is also able to ride by itself along the space station arm's railway.

The crew will finish building Dextre during a third spacewalk, set for Monday night. A total of five spacewalks are planned for Endeavour's nearly two-week visit to the space station, the most ever performed during a joint shuttle-station flight.

With files from the Associated Press