Honda Motor Co., aiming to expand its range of low-pollution autos in the United States, is studying ways to boost sales of natural-gas-powered Civics to capitalize on consumer interest in a gasoline alternative.

The company sells only about 1,000 Ohio-built Civic GX sedans a year in California and other states with natural-gas fuel stations open to the public, said John Mendel, executive vice president of Honda's U.S. sales unit. Sales could rise to 10 times that level, he said, without giving a specific target.

''We're looking very strongly at that,'' Mendel said. ''As you saw us expand Civic GX beyond California, we're looking at plans to expand it further.''

Natural-gas autos, sold by many carmakers in the 1980s and 1990s, fell from favor in the past decade because of federal fuel-economy credits for less costly ethanol-powered models, a drop in gasoline prices and the volatile cost of natural gas. The GX currently is the only natural-gas model still sold directly to consumers by a major auto manufacturer.

The compact sedan travels about 220 miles when fully fueled with the equivalent of eight gallons of natural gas. The company built 1,000 of the cars in East Liberty in 2007, and plans to make at least 1,100 this year, spokesman Ed Miller said.

By comparison, Honda sold 32,575 Civic Hybrids to U.S. customers last year, and Toyota Motor Corp. recorded 277,750 such hybrid sales, led by the Prius. Hybrid gasoline-electric vehicles increase fuel efficiency by combining a battery-powered electric motor and a gasoline engine.

Honda and Toyota share top U.S. fuel-efficiency rankings. Honda this year will begin leasing hydrogen fuel-cell Clarity sedans in California and in 2009 will add its first U.S. diesel model to help improve the efficiency of its fleet.

The U.S. Environmental Protection Agency rates the GX as the cleanest internal-combustion engine auto ever tested, and the American Council for an Energy-Efficient Economy this month named the model ''America's greenest car.''

Demand for the vehicles is still low because buyers don't see a big enough advantage over gasoline-fueled cars, said Don Hillebrand, director of Argonne National Laboratory's Center for Transportation Research in Argonne, Illinois.

Natural-gas fuel tanks crowd out trunk space, and need to be refilled more frequently, Hillebrand said. He also said there aren't enough stations.

The GX's carbon-fiber fuel tank and modified engine raise its base price to $24,590, $1,990 more than the Civic Hybrid.