WALLOPS ISLAND, Virginia (AP) — A private company contracted by the U.S. space agency to make supply runs to the International Space Station called off a test launch of an unmanned rocket, saying an important data cord linked to the rocket's second stage detached too soon.

The Antares rocket had been scheduled to blast off Wednesday afternoon from Virginia when the countdown clock was halted 12 minutes before the expected launch.

Barron Beneski, a spokesman for Orbital Sciences Corp., said officials would try again no sooner than Friday afternoon, though no date was immediately announced.

Orbital crews were examining the rocket to determine how the ethernet cable came loose. Orbital officials initially had said they suspected high winds.

At the time the cable separated, the winds were blowing less than 7 mph (11 kph), said Frank Culbertson, executive vice president and general manager of Orbital's Advanced Programs.

"They were really light," he said. "You know, we don't know if it was something blowing in the wind or a big sea gull."

Orbital was one of two companies, along with competitor SpaceX, chosen to supply the space station by NASA, which ended its three-decade-old shuttle program in 2011.

SpaceX was awarded a $1.6 billion contract by NASA in 2006 to make a dozen restocking missions. SpaceX has linked up with the space station three times. In 2008, Orbital jumped in and was awarded a $1.9 billion contract for eight deliveries.

"We've been playing catch up, but we're about caught up," Culbertson said recently. "By the end of next year we should have an additional four or five cargo missions under our belt, so we're going to be moving fast."

Wednesday's planned launch was designed to test whether a practice payload could reach orbit and safely separate from the rocket.

If ultimately successful in testing Antares, Orbital executives have said they hoped to launch a rocket this summer carrying its Cygnus cargo ship aloft to see whether it could safely dock with the space station.

Orbital is under contract to eventually deliver about 44,000 pounds (19,950 kilograms) of supplies to the space station and envisions making about two deliveries per year.

Unlike the SpaceX's Dragon capsule, which is capable of two-way deliveries, the Orbital cargo ship is not designed to return with experiments or other items from the space station. Instead, Orbital's plans call for filling its Cygnus ship with garbage to be incinerated with the craft upon re-entering Earth's atmosphere. That's also what Russian, European and Japanese cargo ships do.