Astronauts flexed the giant arms of the international space station's new robot for the first time, testing the brakes and maneuvering the appendages into position for a Monday night spacewalk.

All the brakes on the Canadian-built robot passed the test except for one in the wrist joint of its left arm.

That brake slipped a tad more than engineers wanted, but officials weren't concerned about the performance of the robot, called Dextre.

"In the long term it's not going to affect the operation of Dextre in any significant way," said Pierre Jean, Canada's acting space station program manager.

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Astronauts Richard Linnehan and Robert Behnken planned to spend Monday's spacewalk adding a tool holster and other accoutrements for Dextre, which is designed to assist spacewalking astronauts maintain the station.

They were hoping for a less challenging outing than Linnehan and fellow spacewalker Michael Foreman endured over the weekend to install Dextre's 11-foot arms.

The pair had to use a pry bar and brute force to free one of the arms from the transport bed where it was latched down for launch.

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Still, Foreman said his first spacewalk was one of the most "rewarding, exhilarating and difficult" experiences of his life.

Linnehan said it has been surreal to work around the giant white robot, which he said reminded him of a prop from a Star Wars movie.

"But it isn't sci fi, it's reality and it's happening up here right now," he said.

Dextre — short for "dexterous" and pronounced like Dexter — could someday take over some of the tougher chores from spacewalkers, like lugging around big replacement parts.

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.

While some of the astronauts prepared for Monday night's outing, other crew members stowed equipment that was brought to the station aboard the storage compartment segment of Japan's Kibo lab.

That will pave the way for the shuttle Discovery to deliver the $1 billion lab in May.