Florida ? NASA on Friday delayed the liftoff of space shuttle Atlantis until Sunday at the earliest and said it might tighten the launch rules, at astronauts’ request, to cope with unreliable gauges in the fuel tank.

During a nearly six-hour meeting, representatives of NASA’s astronaut office proposed that the launch proceed only if all four of the hydrogen fuel gauges and their associated systems work properly. The launch rule currently calls for only three good gauges.

Shuttle managers said they would meet again today to decide whether to accept that proposal and proceed.

“We pretty much came to the conclusion that … we have got a suspect system,” shuttle program manager Wayne Hale said.