CAPE CANAVERAL, Fla. — NASA delayed the launch of space shuttle Endeavour today because of a hydrogen gas leak similar to one that cropped up three months ago.

The countdown was halted shortly after midnight, about 2½ hours into the fueling of the external tank and less than seven hours before the launch. The astronauts had not yet suited up.

Mission managers planned to meet later this morning to decide when to try another launch attempt for the space station construction mission.