The tentative plan is to have Commander Gennady Padalka and Flight Engineer Michael Fincke try again, as early as Tuesday. But that can't happen until NASA and Russian engineers are sure what caused the oxygen readings for Fincke's suit to drop rapidly, alarming controllers in Moscow.

The crew worked Friday with colleagues on the ground in Houston and Moscow to troubleshoot the problem with one of the Orlan spacesuits aboard the station. The crew is left with three Orlan suits unless the one Fincke wore Thursday night can be repaired.

The American spacesuits on board already are out of order. Two of three are broken, so the set can't be used until repair parts are sent tospace station.

The repair spacewalk must be rescheduled. The men did not get to start their task: restoring power to a critical steering gyroscope that stopped working April 21. The station is being controlled by two working gyroscopes, the minimum needed to keep it properly positioned.

Without them, Russian thrusters and fuel would have to be used. There's enough propellant on board to control the station for about six months if another gyro fails, but NASA and Russian officials do not want to wait around for that to happen.

Mission managers will meet in Houston on Monday to review what happened and decide when to reschedule the repair job.

The crew is being told to work toward a spacewalk Tuesday.