Air Force officials have postponed launching the Titan 4 rocket one additional day -- to the predawn hours of Thursday -- as technicians catch up on pre-flight activities impacted by last week's nitrogen tetroxide leak at Cape Canaveral's Complex 40.

The rocket's classified mission will place a secret national security payload into orbit.

Work to clean up the spill, repair the ground support equipment that caused the leak and return to countdown preparations have put launch preparations on a tight schedule.

The launch window is a secret, but liftoff will occur sometime between 0340-0900 GMT (11:40 p.m. EDT Wednesday and 5 a.m. Thursday).

The weather forecast for Thursday's launch opportunity calls for an 80 percent chance of favorable conditions. See the full forecast here.