The problem that forced astronauts aboard the international space station to abort Thursday night's spacewalk was a manually operated auxiliary switch in Edward "Mike" Fincke's spacesuit that locked in the open position, officials said yesterday.

NASA spokesman Rob Navias said in a telephone interview that Russian engineers believe the malfunction in the switch, which increases the flow of oxygen, can be easily overcome with a quick check before Fincke, the American crew member, leaves the space station's airlock when the spacewalk is rescheduled.

Navias said NASA and the Russian Space Agency have decided that Fincke can wear the same Russian Orlan spacesuit when he and station commander Gennady Padalka next try the spacewalk, scheduled to happen no sooner than Tuesday, Navias said.

The spacewalk, undertaken to replace a faulty circuit breaker that shut down one of the station's four main gyroscopes two months ago, ended 14 minutes after it began when Russian mission control noticed that Fincke's bottled oxygen was depleting too rapidly. The controllers ordered Fincke and Padalka back inside the station and aborted the mission.

After "troubleshooting throughout the night," Russian engineers determined that the manually operated valve apparently "failed to seat properly" after Fincke tested it, Navias said. As a result, the valve was letting extra oxygen escape into the suit from Fincke's supply.

"The mechanism is called an injector," Navias explained. "The crew members use them outside if they feel too warm, or if the ground tells them pressure is too low. Pulling a lever on the outside of the suit enables a higher flow of oxygen through the suit."

Both Fincke and Padalka tested their injectors Tuesday during preparatory procedures, Navias said. "When you activate the system, there's a light on the helmet that tells the other crew members that the system is operating," he said.

Both lights went on and both lights went off when the astronauts pushed the levers down, Navias said, but oxygen from Fincke's bottle continued to flow.

Navias said the Russians think the problem can be resolved by making an additional check of the valve lever before the astronauts disconnect from the station's oxygen supply. The mission management team will make a final decision Tuesday on how to proceed with the spacewalk.

U.S. astronaut Mike Fincke, on his first spacewalk, was ordered back inside the space station minutes after leaving the airlock.