NASA has delayed yet again the fourth spacewalk of U.S. shuttle Discovery's two-week mission to boost the capability of the International Space Station. The walk, originally set for Thursday, was first moved to Friday and is now scheduled for Saturday. It will focus on a tear in one of the station's solar wings. Officials say fixing that problem is the mission's top priority. VOA's Alex Villarreal reports from Washington.

Shuttle and station crew members are busy preparing for the mission's next spacewalk, pushed back for a second time to Saturday.

On Wednesday, officials changed the priority of the spacewalk from inspection of a malfunctioning rotary joint on one side of the station to repair of a torn solar wing on the other.

The problems with the wing and the rotating joint could delay future missions. The parts are needed to generate the power to support new equipment.

Space station program manager Mike Suffredini said the first thing astronauts need to do is fix the wing.

"We believe we are in a condition where we could over time tear the blanket further, and if we tear the blanket, if we do enough damage to the blanket, we could potentially get in a configuration where we couldn't stabilize the array," said Mike Suffredini. "And if we can't stabilize the array, we'll have to figure out what to do about that, and we don't have a lot of options."

Preparations for Saturday's spacewalk include studying procedures, building tools and re-sizing a space suit glove.

During the walk, Discovery crew member Scott Parazynski will be raised on the end of a long extension pole grasped by the station's robotic arm. This configuration will allow him to reach the solar wing and investigate the problem. Fellow crew member Doug Wheelock will guide arm operators as they maneuver Parazynski.

Crews spotted the tear in the wing as they unfurled it on Tuesday. The tear forced NASA to halt the process before the wing was fully extended.

Crew members took photos of the damage and sent the images to engineers on the ground for analysis. NASA officials say they will not know how to fix the wing until they determine the cause of the tear.

Speaking to reporters Wednesday, Discovery Commander Pam Melroy said crew members remain confident despite the setbacks. She said they are ready to do whatever is needed.

"You never know what is going to happen every morning when you wake up," she said. "And I think what is holding us up together and keeping us all upbeat is that we are all doing something that we believe in so strongly and that we love and we are having a ton of fun together doing it. And so we feel confident that whatever comes, we are going to be able to handle it."

NASA officials say as of now, the torn solar wing is stable and seems to be delivering all its power. But in order to sustain two new laboratories to be added later, it needs to be fixed.

Discovery's two-week mission aims to expand the size of the space station to make way for the European and Japanese modules.

NASA extended the mission by one day to allow for further inspection of the rotating joint. Officials say that inspection might now occur during a later mission.

Discovery is set to undock from the station on Monday, Nov.5. The shuttle will return to Earth on November 7.