Last-minute concerns over welds in critical fuel lines forced NASA today to delay space shuttle Discovery's rescue mission to the Hubble Space Telescope for one more day.

It was the seventh postponement for Discovery, which should have flown in October. And it was especially frustrating because engineers believe the welds on the shuttle's 20-year-old fuel lines are good.

They said they simply need time to review all the paperwork and X-rays to confirm that.

"We probably could have launched. It would have been just fine," said shuttle program manager Ron Dittemore. "But we don't do that without knowing for sure."

Liftoff is set for 8:47 p.m. Friday.

Bad weather, though, was forecast, with a 60 percent chance that rain or low clouds could interfere.

If the shuttle is not up by Saturday night, the flight will have to be bumped into January because NASA does not want to fly close to New Year's and run the risk of Y2K trouble.

In California, the launch of a NASA satellite that will study Earth's environment was automatically halted by a computer moments before liftoff today, and the space agency said it was not immediately clear what caused the cutoff.

NASA said it will probably try again in 24 hours to launch the Terra satellite.