Unexpected delays in assembling Discovery's solid fuel booster rockets probably will hold up the first post-Challenger shuttle mission at least 10 days beyond the planned liftoff, NASA says.

The space agency will not officially make a decision on a new date until after the assembly process is further along, said Arnold D. Aldrich, shuttle program director.

But he said Tuesday at the 25th Space Congress in nearby Cocoa Beach, "we're down probably 10 days on the projected Aug. 4 launch date."