NASA is planning to launch the shuttle Discovery to the International Space Station on March 12. Discovery is now slated to launch no earlier than March 12 at 8:54 p.m. EDT, one month later than planned, on a two-week construction flight to the space station. The mission has been delayed several times due to concerns with the shuttle's fuel control valves.

The shuttle must launch by March 13 to complete its mission without obstructing the flight of a Russian spacecraft scheduled to arrive at the space station on March 28. The Discovery's flight is the first of six that NASA has scheduled for this year.

One valve on shuttle Endeavour failed in flight in November without incident. Since then NASA has been working overtime to determine why it broke and what could happen if one broke again.

"The space shuttle program will hold a meeting March 4 to review new data and assess ongoing work. Managers then will determine whether to move forward with a flight readiness review March 6," an agency news release said.

NASA initially planned to launch Discovery on Feb. 12, but has delayed the mission four times because of fuel control valve safety concerns. The most recent delay, announced last Friday, left Discovery without a firm launch target. NASA engineers now think valves that have flown on fewer flights are less susceptible to cracking and breaking. So teams at KSC on Wednesday started to replace the flow-control valves now aboard Discovery with newer ones.