The latest Air Force weather forecast offers a 70-percent chance of conditions good enough for liftoff during the one-hour window, with cumulus clouds and showers again the main concern.

Heavy clouds moving in from the Atlantic Ocean scrubbed a first launch attempt Wednesday.

A second attempt was planned this morning, but a leak from fuel line at Cape Canaveral Air Force Station's Launch Complex 17B prompted another delay.

Engineers traced the leak to a corroded weld, located beneath the launch pad, in the line through which nearly 10,000 gallons of RP-1 rocket fuel will be pumped from a storage tank to the rocket.

The weld was repaired quickly enough to limit the delay to one day, and NASA says the rocket and spacecraft are ready to fly.