NASA has cancelled Tuesday's Atlantis shuttle launch but put off a decision on sheltering the orbiter from Tropical Storm Ernesto, a move that would prevent a flight this week, a spokesman said Monday.
The US space agency will keep a close eye on Ernesto's development in the Caribbean to see if it can possibly leave Atlantis on its Florida launch pad to ride out the storm.
NASA wants to keep alive its goal of launching the shuttle by September 7 on the first International Space Station construction mission since the 2003 Columbia disaster. No possible new launch date has been set.
Pulling the shuttle off its launch pad and back to its massive hangar would make it nearly impossible to meet that deadline. Launching after that date would require negotiations with Russia as it would conflict with a Soyuz rocket mission.
"If they decide to weather the storm on the pad, depending on what kind of effects the storm has on the KSC (Kennedy Space Center) area and the systems at the pad, we could potentially get back up and launch within a few days," said NASA spokesman Kelly Humphries.
Forecasts showed that Ernesto could regain hurricane strength and strike southern Florida Wednesday.
NASA has taken preliminary steps to remove the shuttle from the launch pad and will make a final decision on moving it by midday Tuesday, officials said.
Weather-related events have frustrated NASA's bid to launch on the first ISS construction mission in nearly four years.
Officials had already cancelled launches on Sunday and Monday to give engineers more time to determine whether a strong lightning strike on Friday had damaged ground and shuttle systems.
The orbiter was cleared of damage late Sunday.
If it fails to fly this month, the next launch opportunity is in late October.
Once it launches, Atlantis will carry six astronauts and a new 16-tonne segment with two huge solar panels for the half-finished space station.