More than a year after they were introduced, federal rules intended to keep cell phone towers operating during natural disasters remain in limbo.

A federal appeals court on Tuesday put off deciding on the wireless industry's challenge to the regulations until the Federal Communications Commission gets preliminary clearance for the rules.

After a panel of experts appointed by the FCC pointed out that many cell towers along the Gulf Coast stopped working when they lost power during Hurricane Katrina, the agency proposed in May 2007 that all cell towers have a minimum of eight hours of backup power that would switch on in the event a tower lost its regular energy source.

The loss of power contributed to communication breakdowns that complicated rescue and recovery efforts during the 2005 disaster.

Wireless companies have said the regulations were illegally drafted and would present a huge economic and bureaucratic burden. In particular, they said, the thousands of generators or battery packs required would be expensive and local zoning rules or structural limitations could make installation impossible in some places.

The FCC agreed in October to exempt cell sites that a wireless carrier proved couldn't meet the rules. The FCC would give companies six months to report on the feasibility of installing backup power and another six months either to bring sites into compliance or explain how they would provide backup service through other means, such as portable cellular transmitters.

CTIA-The Wireless Association, Sprint Nextel Corp. and others asked the U.S. Court of Appeals in Washington, D.C., this year to intervene, saying the exemptions would still leave wireless companies scrambling to inspect and compile reports on thousands of towers.

The appeals court put the rules on hold while it heard each sides' arguments in May.