NASA moved the Atlantis shuttle off its Florida launch pad on Tuesday to protect it from tropical storm Ernesto, a change that threatens plans to lift off this month.
No new date was set to launch Atlantis on the first International Space Station (ISS) construction mission since the 2003 Columbia shuttle tragedy.
The US space agency had already cancelled Tuesday's launch but delayed its decision to move Atlantis back to its massive hangar until the last minute on the off chance that dramatic changes to the storm's path would occur.
Atlantis' massive mobile platform started crawling on a 10-hour trip back to the vehicle assembly building at the Kennedy Space Center on Florida's east coast. The storm is forecast to hit southern Florida by late Wednesday.
"The rollback is a decision to slip launch by a couple of weeks," said NASA spokesman Bruce Buckingham. It takes about eight days to prepare the shuttle for lift-off once it is back on its launch pad.