STS-103 astronauts talk to reporters after arriving at Kennedy Space Center on Monday. Photo: NASA TV/SPACEFLIGHT NOW

Yet another damaged electrical wire has been found aboard shuttle Discovery and NASA officials say the problem will probably delay again the star-crossed mission to service the Hubble Space Telescope.

The U.S. space agency disclosed the problem late Monday as the seven Discovery astronauts flew from their home base in Houston to Kennedy Space Center to begin final pre-flight preparations.

"It is great to be here," lead spacewalker Steve Smith told reporters after landing. "Hubble needs us, the four spacewalkers are ready to go, so we will be up there shortly."

For now, Discovery officially remains scheduled for launch Saturday at 12:13 a.m. EST (0513 GMT), the start of a 38-minute window to rendezvous with the orbiting Hubble observatory.

But the mission is expected to be delayed 24 hours to replace a damaged engine cable. The next chance to launch Discovery would come at 11:42 p.m. EST Saturday (0442 GMT Sunday), the opening of a 42-minute window.

Workers making final inspections inside the shuttle's aft engine compartment discovered a 1/8th-inch nick in the insulation on a command and feedback cable attached to main engine No. 2, NASA spokesman Joel Wells said.

The wiring must be replaced and engine tests re-performed before the aft compartment can be locked up for launch.

"Preliminary reports do indicate a possible one-day slip in the launch date," Wells said.

Officials are expected to determine by Tuesday when Discovery could be ready for launch.

This latest glitch adds to a list of wiring troubles and other workplace incidents that have delayed Discovery's mission from mid-October.

The problems began in July when a wiring short-circuit knocked out two of Columbia's engine controllers seconds after liftoff. That prompted the shuttle fleet to be grounded for wiring inspections.

In addition, workers spent the weekend looking at wiring that was inspected previously but had to be re-examined due to a paperwork snafu.

The engineer that made the earlier inspection and repair failed to document the action, making space agency officials unsure if the work was really completed.

The second look revealed the wiring was indeed inspected and fixed, NASA spokesman Bruce Buckingham said.

That weekend work alone used up all of the extra time NASA had left in the pre-launch schedule to deal with problems, Well said.

Discovery will spend 10 days in space with its astronauts completing four spacewalks to install six fresh gyroscopes to restore Hubble's crippled pointing system to working order. Other work will include replacing aging electronics and added new thermal insulation to the 9 1/2-year old telescope.

In addition to Smith, the other shuttle crewmembers are commander Curt Brown, rookie pilot Scott Kelly, robot arm operator Jean-Francois Clervoy and spacewalkers John Grunsfeld, Michael Foale and Claude Nicollier.