Space shuttle Endeavour's flight to the international space station is off until next week because of a Russian cargo ship that is hanging from the orbiting complex without a firm grip.

Shuttle managers canceled Thursday's liftoff of Endeavour because of danger from the unmanned supply ship and later ruled out Friday, too.

In a series of meetings Friday morning, they decided to aim for a launch Tuesday, following a spacewalk by a pair of cosmonauts at the space station to fix the problem. The outing is set for Monday.

The supply ship pulled up at the space station on Wednesday but failed to attach itself securely. NASA feared the forces exerted by the arriving shuttle would cause the supply ship to wobble, damaging the space station.

The launch of Endeavour and the seven-member crew was scrubbed with just hours left in the countdown as space agency managers tried to diagnose the trouble and decide what to do.

"We need to develop a plan and make sure that we can support it ... and that we don't, in the process, make something worse," said NASA's Jim Van Laak, a space station manager.

Endeavour is supposed to drop off two Americans and one Russian for a six-month stay aboard the space station, and bring back the three men who have been living up there since August.

The countdown had been surrounded by unprecedented security, with fighter jets, attack helicopters and military personnel in camouflage on guard against terrorist attacks. A 35-mile no-fly zone on small planes was established around the launch pad. Air Force officials said similar security would be in place next week.

The supply ship arrived at the space station with more than a ton of food, fuel, clothes and other supplies. But the eight docking latches that are supposed to hold it securely did not click into place.

The supply ship cannot be opened until it is securely attached to the space station.

Based on a fuzzy video of the docking, flight controllers suspect a 1-foot cable -- or something else entirely -- is preventing the ship from latching on. But no one seemed to know where the cable came from.

"As different people look at the video, some say, `Oh, there it is,' and they clearly point to a piece of debris. And other people say, `I've no idea what you're pointing to,"' Van Laak said.

Russia proposed that the two cosmonauts aboard the space station, Vladimir Dezhurov and Mikhail Tyurin, go out on a spacewalk Monday morning to remove the debris.

The question for NASA was whether it would have been better for Endeavour to wait on the launch pad until the repair is completed, or proceed with liftoff and fix the problem after the shuttle arrives.