Even though the countdown for the Saturday launch of space shuttle Endeavour at 7:39 p. m. has already been started, yet the launch is uncertain due to stormy weather. Air Force forecast revealed fears regarding showers and heavy clouds wandering within twenty nautical miles of Kennedy Space Center, signifying only 40 percent chances of Saturday launch.

However, the chances for launching improved to 60 percent on Sunday and 70 percent on Monday.

Last month, Endeavour launch was postponed because of hydrogen gas leak.

Endeavour is going on its 16-day mission in which seven astronauts have been assigned the task of installing the final piece of Japan's lab at the international space station.

The crew members include, Commander Mark Polansky, pilot Doug Hurley and mission specialists Chris Cassidy, Tim Kopra, Tom Marshburn, Julie Payette and David Wolf.

NASA test director, Charlie Blackwell-Thompson and shuttle weather officer, Kathy Winters, will discuss the issue at a briefing.