Running behind schedule, engineers are working through a series of tests to ready the shuttle Discovery for its trip to the launch pad Sunday and blastoff on the first post-Challenger mission in early September.

A NASA statement said Tuesday Rear Adm. Richard Truly, associate administrator for space flight, "updated the target for the upcoming shuttle launch to early September" after a "major review" of the shuttle program. Launch had been targeted for around Aug. 22.A specific date was not announced but as of Monday, internal planning schedules showed Sept. 4 as the current target for blastoff based on the amount of work completed so far in Discovery's launch processing.

But the schedule has been changing on a daily basis and a firm launch date is not expected to emerge until well after the orbiter reaches the launch pad.

Top NASA managers, meanwhile, planned to meet in Washington today to discuss the agency's budget and to review the overall status of launch preparations.