CAPE CANAVERAL, Fla. —  NASA called off Thursday's launch of space shuttle Atlantis after a pair of fuel gauges in its big external tank failed to work properly, a recurring problem ever since the Columbia disaster.

Shuttle managers said the next launch attempt would be no earlier than Saturday.

Preliminary indications were that the problem might be with an open circuit rather than the gauges themselves — perhaps a spliced line or bad connector — which would be easier to fix.

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Mission managers met well into the evening, debating how best to proceed with the countdown. They decided to forgo a Friday launch attempt to give engineers more time to figure out what was wrong and resolve the trouble.

"We need more time," said LeRoy Cain, chairman of the mission management team.

Launch director Doug Lyons said he was hopeful the launch team would get another crack at getting Atlantis off the pad before the end of next week. Because of poor sun angles and computer concerns, NASA would have to wait until the beginning of January to launch Atlantis and the European Space Agency's space station lab, Columbus, if they aren't flying by next Thursday or Friday.

The fuel tank sensors are part of a critical backup system to ensure that the shuttle's three main engines don't shut down too soon or too late during liftoff, a potentially catastrophic problem. Trouble with the sensors have delayed shuttle launches before, most recently in September 2006. The trouble began cropping up following the Columbia disaster.