SpaceX has called off its flight to the International Space Station.

The unmanned Falcon rocket was supposed to blast off before sunrise Tuesday. But the countdown was halted with just one minute remaining. The soonest SpaceX can try again is Friday. No reason was immediately given for the launch abort.

The Dragon capsule aboard the rocket contains more than 5,000 pounds of supplies and experiments ordered up by NASA. That's the primary objective for SpaceX. But the California-based company was to attempt an even more extraordinary feat once the Dragon is on its way: flying the booster rocket to a platform in the Atlantic. No one has ever pulled off such a touchdown.

SpaceX's billionaire founder Elon Musk says recovering and reusing rockets could speed up launches and drive down costs.