Space shuttle Endeavour's launch is off until probably the end of the week.

On Sunday, NASA officials said there was no way Endeavour could blast off Monday on its final voyage. A new launch date was not set. But officials said it appeared that the work needed to repair a faulty heater system in the shuttle would push the launch to the end of the week, at best.

Endeavour's commander, Mark Kelly, is married to Rep. Gabrielle Giffords. She arrived at Kennedy Space Center last week in hopes of seeing her husband rocket into orbit. But Friday's launch attempt was called off because of the heater trouble.

A NASA spokesman says technicians and engineers will replace a switchbox in Endeavour's engine compartment. Two days of testing are required, for the repair.