U.S. farm groups contend they have sharply reduced use, but are unable to find effective substitute fumigants for grain storage and for crops such as tomatoes, peppers, eggplant, strawberries and sweet potatoes.

The EPA said it asked the U.N. ozone secretariat to allow U.S. farmers in 2005 to use 39 percent of the nation's baseline consumption of methyl bromide. That level is "substantially below" recent consumption, the agency said in a statement.

"Our request will decline to 37 percent in 2006, reflecting our commitment to ozone layer protection and the likelihood that additional alternatives will be registered and available for use by then," the EPA said.

The U.S. request will be considered by a U.N. advisory group, which will make its recommendations in November.

The North American Millers Association has said a total ban on methyl bromide to fumigate grain mills would cost that industry more than $60 million annually. Most of that would be from lost revenues because of having to temporarily close mills to use sanitizers that are slower acting.

Under the U.N. plan, methyl bromide has been phased out with a 25 percent reduction in 1999 and again in 2001. This year, nations are supposed to cut use by 20 percent.

The vast majority of methyl bromide used in the United States fumigates soil before planting crops. About 11 percent is used to fumigate harvested commodities during storage and export, 6 percent is used to destroy bugs in food plants, warehouses and museums, and the remaining 8 percent goes into the production of other chemicals.

The U.S. Agriculture Department said it has spent more than $146 million on research for alternatives to methyl bromide.