The Federal Highway Administration issued an emergency ruling yesterday temporarily lifting length limits on trucks hauling ammunition, reacting to trucker complaints that some states, particularly Maryland and California, were cracking down on enforcement and delaying shipments for the Persian Gulf War.

The ruling did not deal with trucker complaints that some states were also cracking down on weight limits on trucks carrying battle tanks, including a standoff in Louisiana last week when a trucker was forced to load a tank onto a railroad flatcar for the remainder of its cross-country trip.

The FHWA ruling, which came less than two days after it was requested by the trucking industry, is a six-month exemption from length limits on trucks equipped with dromedary boxes -- cargo containers of up to 65 inches attached to the truck frame between the tractor and trailer.

These boxes, which push trucks over length limits in some states, are necessary in hauling some ammunition because bombs and missiles cannot be hauled with fuses attached. Fuses and other ignition devices typically are kept in the dromedary box while bombs and missiles are hauled in a 48-foot trailer.

Tom Boyle, head of T.F. Boyle Transportation of Billerica, Mass., said truckers had experienced problems sporadically, but the problem grew worse with stepped-up shipments for the gulf. He said he had some problems in Massachusetts and Connecticut, but Maryland and California appeared to be lying in wait for ammunition carriers.

John J. Collins, a vice president for the American Trucking Associations, said a number of ammunition shipments have been delayed, and "the concern was it might grow worse."

Drew Cobbs, an assistant to the Maryland transportation secretary, said state police have been told to allow the dromedary trucks to pass. "Under our law, those trucks were not legal," Cobbs said. "We were just basically enforcing our law."