The launch of the space shuttle Discovery is expected to be delayed until early October as a result of plans to repair a fuel leak on the launch pad, space agency sources said on Tuesday. A NASA statement said technicians would cut a hole into Discovery's cargo bay in an effort to cap the two-week-old leak in a steering engine, without rolling the space ship off the launch pad. It acknowledged that the repairs would add one to two more weeks to the launch schedule. Meanwhile, technicians are struggling to fix a leaky nitrogen fuel line and a balky fuel valve that threaten to force another postponement in the test firing of the shuttle's main engines set for Thursday morning.