Workers inspect a foot-long section of a hydrogen line crushed inside shuttle Discovery. Photo NASA Watch

A crushed liquid hydrogen line inside shuttle Discovery's cramped engine compartment has forced NASA officials to delay this weekend's mission to fix the Hubble Space Telescope by at least one day.

The U.S. space agency is planning a meeting Thursday at 1800 GMT (1 p.m. EST) to decide if the star-crossed mission will be delayed even further.

The latest in a seemingly endless list of problems that have kept Discovery grounded on Earth for two months is a damaged four-inch diameter liquid hydrogen recirculation line. The six-foot long line is part of the plumbing running between the shuttle's engines and external fuel tank, and supplies hydrogen to condition the engines for ignition.

Workers found the line was damaged during routine inspections Wednesday. The line was crushed along a 12-inch stretch with some dents one-half-inch deep.

Shuttles have flown with dented recirculation lines before, but in those cases, there was less damage.

If officials decide to replace the line, Discovery's mission would have to be delayed several more days, NASA spokesman James Hartsfield said.

"We are laying out schedules to see what we would be up against," spokesman Bruce Buckingham said.

Shuttle managers had planned to begin the three-day launch countdown on Thursday for liftoff at 0442 GMT on Sunday (11:42 p.m. EST Saturday night).

However, the countdown is on hold pending Thursday's meeting.

NASA officials want Discovery's 10-day mission to be completed by Dec. 27 or 28 to avoid any computer-related problems associated with Y2K.

Scientists are hoping Discovery is launched soon, too.

The orbiting Hubble Space Telescope hasn't been able to make any observations of the universe since mid-November when its precision pointing system shut down.

Discovery's astronauts are slated to install new equipment to fix the pointing system and restore Hubble to working order.