CAPE CANAVERAL, Fla. -- Last-minute rocket trouble forced SpaceX on Saturday to delay its inaugural launch from NASA's historic moon pad.

SpaceX halted the countdown with just 13 seconds remaining. The second-stage steering issue actually cropped up several minutes earlier. But with just an instant to get the unmanned Falcon rocket airborne, flight controllers could not resolve the problem in time.

The next launch attempt -- provided everything can be fixed quickly -- would be Sunday morning.

The Falcon remains at Kennedy Space Center's Launch Complex 39A, waiting to soar on a space station delivery mission. It's the same pad where Americans flew to the moon almost a half-century ago.

Up at the International Space Station, French astronaut Thomas Pesquet had a light-hearted take on the delay.

"Looks like I'll have to wait one more day to get my French cheese ;)" He added: "We need all your cargo for @ISS--Research!"

SpaceX chief Elon Musk said engineers want to make certain the "slightly odd" position of an engine piston isn't representative of bigger trouble. It's not out of the question that Saturday's problem is somehow related to the minor upper-stage helium leak detected the day before, he reported.

There's a 99 per cent chance everything is likely to be fine, Musk said in a tweet. "But that 1 per cent chance isn't worth rolling the dice. Better to wait a day."

Thousands of guests had jammed the space centre to witness the comeback of 39A, last used in 2011 for the final space shuttle flight. Disappointment was high when the urgent call of "hold, hold, hold!" sounded over the radio lines.

This will be SpaceX's first Florida launch since a rocket explosion last summer.

The Sept. 1 accident occurred during prelaunch testing at a neighbouring pad. SpaceX turned to Launch Complex 39A -- which it leases from NASA -- to resume flights. The company hopes to launch astronauts from 39A next year.

Russia, meanwhile, plans to launch a supply ship to the International Space Station on Wednesday. If the SpaceX mission doesn't get going soon, it would likely have to get in line behind the Russian delivery.

Standing down to take a closer look at positioning of the second stage engine nozzle. 9:38am ET tomorrow is next earliest launch opportunity