CAPE CANAVERAL, Fla. (AP) -- A blunder by flight controllers prevented the new international space station from moving out of the way of dangerous space junk. The rocket debris ended up passing at a safe distance.

NASA said the sequence of computer commands sent up by flight controllers to fire the station's engines over the weekend failed because of human error. It disclosed the incident Thursday.

Initially, the U.S. military organization that tracks objects in space predicted the rocket chunk would pass within two-thirds of a mile of the space station on Sunday. It ended up coming no closer than 4 1/2 miles.

The debris was Russian in origin and fairly large, although its exact dimensions were not immediately known. A collision could have destroyed the empty outpost, which has been in orbit for only seven months. The first residents are not due to arrive until next spring.

At last count, the U.S. Space Command in Colorado Springs, Colo., was tracking more than 8,700 manmade objects in orbit, most of that junk. With an orbital speed of 17,500 mph, any one of them could do serious damage to the space station, which consists of only two compartments so far.

Measures already have been taken to prevent this from happening again, said Frank Culbertson, NASA deputy program manager for space station operations.

"I'm very glad we learned what we learned at this point in the mission before we have more hardware up there and before we have people up there," Culbertson said. But he noted that if astronauts had been aboard, they could have maneuvered the space station more easily than ground controllers.

The maneuvering command, drawn up by both U.S. and Russian engineers, was sent from the Russian control center outside Moscow on Saturday night. But the command contained faulty instructions, and the space station's computers rejected it. The station was left without motion control for an entire orbit.

Flight controllers may not have factored in the changes in the space station's mass and center of gravity since shuttle Discovery delivered 2 tons of gear earlier this month, or else the changes were entered incorrectly.

Culbertson said it wasn't immediately clear whether Americans or Russians were to blame.

By the time flight controllers learned of their mistake, it was too late to send up a corrected command. "But because the probability was low, we weren't too worried about it," Culbertson said.

In any case, the Space Command soon revised the projected distance between the two objects from 0.6 miles to 4 1/2 miles.

It is the second time in less than three months that NASA has reported an erroneous station command. In late April, Russian flight controllers mistakenly ordered a motor to turn on and move the space station's solar wings; onboard computers detected the error and shut off power to the motor.