U.S. firm SpaceX canceled its planned flight to the International Space Station (ISS) at the last minute on Tuesday because of technical trouble.

The unmanned Falcon rocket, carrying a Dragon cargo ship for the ISS, was due to lift off from Cape Canaveral Air Force Station before sunrise. But the countdown was halted with just over a minute remaining after engineers spotted a problem with a piece of equipment in the rocket’s upper-stage engine.

The soonest SpaceX can try again is Friday morning, provided it can fix the problem by then.

SpaceX officials said one of two motors needed for rocket thrust steering of the second stage failed to operate as expected. If controllers had not aborted the launch, computers likely would have done so closer to liftoff, officials said.

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

If successful, the test will mark a significant step in the company’s quest to develop rockets that can be refurbished and reflown. SpaceX's billionaire founder and chief executive, Elon Musk, has said that recovering and reusing rockets could speed up launches and drive down costs.

“If you were to throw the airplane away after every trip you take it’s going to be expensive,” SpaceX vice president Hans Koenigsmann, told reporters at a prelaunch press conference. “This would have an impact on the entire industry.”

The delivery was supposed to be before Christmas, but it was delayed because of a flawed test firing of the rocket engines. The test was repeated successfully, paving the way for Tuesday’s attempt.

SpaceX is one of two companies making cargo runs to the ISS for NASA under contracts worth a combined $3.5 billion.

NASA’s last contracted shipment was destroyed in October in an explosion seconds after liftoff. The company running that mission, Orbital Sciences Corp., has grounded its rocket fleet until later this year.

Wire services