KANSAS CITY, Mo. (AP) -- More than a year after they were first introduced, federal requirements aimed at making sure cell phone towers continue operating during natural disasters remain in limbo.

A federal appeals court on Tuesday put the wireless industry's challenge of the regulations on hold until the Federal Communications Commission gets clearance for the cell tower policy to go into effect.

The FCC proposed in May 2007 that all cell towers have a minimum of eight hours of backup power, which would switch on in the event a tower lost its regular energy source.

The requirement came after a panel of experts appointed by the FCC pointed out that many cell towers along the Gulf Coast lost power following Hurricane Katrina, contributing to communication breakdowns that complicated the rescue and recovery efforts.

Wireless companies have objected to the regulations, claiming they were illegally drafted and would present a huge economic and bureaucratic burden.

In particular, they said that adding generators or battery packs to thousands of cell sites would be expensive and, because of local zoning rules or structural limitations, impossible in some places.

The FCC agreed in October that it would exempt cell sites from the rules, but only if the wireless carrier provided paperwork proving the exemption was necessary.

The FCC would give companies six months from when the rules went into effect to submit those reports and another six months to either bring the sites into compliance or explain how they would provide backup service to those areas 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., to intervene earlier this year, 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.

On Tuesday, it noted that the FCC has yet to get clearance for the rules from the Office of Management and Budget, which is required to sign off on federal regulations whenever they involve mandating members of the public to collect and submit information.

"Because none of the backup power rule's requirements takes effect until OMB approves the information collections, the case is unripe and we shall hold it in abeyance pending OMB's decision," the court wrote.

A spokesman for the FCC didn't immediately return a phone call for comment.

Joe Farren, a spokesman for CTIA, said his organization was "pleased with the court's decision to keep the stay in place while the FCC completes its work on this item."