CAPE CANAVERAL, Fla. (AP) _ An alarm went off just before a rocket was to blast off Saturday with NASA's comet-chasing Stardust spacecraft, indefinitely delaying the launch.

The Boeing Delta rocket was scheduled to blast off at 4:06 p.m. with the Stardust spacecraft. A few minutes before liftoff, however, a dip in current was detected from a rocket radar beacon and a red alarm went off.

The beacon is needed to track the rocket during liftoff.

A new launch date was not immediately announced.

NASA has only one second each day, through Feb. 25, to launch Stardust to Comet Wild-2. The spacecraft is supposed to meet up with the comet in 2004 and bring back samples of the comet in 2006.

It is the first U.S. mission devoted to a comet.