NASA has delayed the fourth spacewalk of a complex two-week mission by U.S. space shuttle Discovery to boost the capability of the International Space Station. The walk, originally set for Thursday, is now scheduled for Friday. 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.

NASA originally scheduled a spacewalk on Thursday to inspect a malfunctioning rotary joint on the right side of the station. The joint is needed to keep the station's solar wings turned toward the sun for power.

But space station program manager Mike Suffredini said the tear in a solar wing on the other side of the station is a much more urgent problem.

"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."

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.

Suffredini said the first thing astronauts need to do is fix the wing.

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.

Earlier 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," said Pam Melroy. "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 operate on the station long-term, it needs to be fixed.

Astronauts will prepare for Friday's spacewalk on Thursday. The walk will be pushed back to Saturday if they are not ready.

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

Discovery's two-week mission aims to expand the size of the space station to make way for European and Japanese scientific laboratories to be installed later.

NASA extended the mission by one day to allow for further inspection of the rotating joint.

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