NATIONAL BRIEFING / FLORIDA

NASA has delayed the launch of the shuttle Discovery for a fourth time amid valve concerns.

After meeting at Kennedy Space Center in Florida, shuttle managers decided against launching in a week.

The launch had been targeted for no sooner than Feb. 27; it was not immediately known when it might be rescheduled.

NASA had hoped to send Discovery to the International Space Station on Feb. 12, but extra tests were ordered for the valves that control the flow of hydrogen gas into the external fuel tank during liftoff. One of those valves broke during the last shuttle launch, in November.