California loves cars, with more on the road than anywhere else in the country. But the state where the Beach Boys wrote odes to the "Little Deuce Coupe" and "409" struggles to balance romance with environmental responsibility, and now California regulators have come up with a new clean-air guideline that has automakers howling.

The state wants to cut vehicles' output of carbon dioxide by 30 percent over the next decade, limiting a major greenhouse gas thought to contribute to global warming. It's the first U.S. attempt to address the controversial issue through car emissions, and automakers argue it could boost car and truck prices nationwide without producing much benefit.

Unlike other engine emissions, carbon dioxide can't be filtered away, so the only way to cut it back is to improve efficiency -- increasing the distance a car can go on a gallon of gasoline. California regulators estimate that achieving their goal would cost roughly $1,000 per vehicle, but carmakers say that figure is low.

"We would certainly consider it one of the most, if not the most, comprehensive and costly environmental programs that's ever been adopted -- not just by California, but by anyone," said John M. Cabaniss Jr., director of environment and energy at the Association of International Automobile Manufacturers, a trade group representing 17 companies including Toyota Motor Corp., Nissan Motor Corp. and Honda Motor Co.

Automakers say the proposed regulation pushes technology further than currently possible and have threatened to sue over what they say is California's attempt to usurp the federal government's authority to set fuel efficiency standards. The state views it as an emissions issue, which is under California control, even though the proposed standards would force cars and trucks to get better gas mileage.

The stakes are high, not only because California accounts for roughly 12 percent of cars and trucks on the road in the United States, but also because it is the cradle of American car culture. From drive-ins to hot rods, from freeways to movie chase scenes, California has long set the pace for how the country relates to its automobiles.

New York, New Jersey and five New England states have auto emissions guidelines modeled on California's and could copy the current action. What's more, the Canadian government is considering stricter fuel efficiency standards in a bid to cut down on greenhouse gases.

"There is a trend," said Dan Becker of the Sierra Club, which has lobbied for the new greenhouse gas standards. "What California is proposing is to slash global warming emissions from automobiles, which is good for California and good for the world. Because they tend to set the pattern for pollution rules nationwide, I suspect more than just the seven [other] states would adopt it."

In the 1990s, the state almost single-handedly began an electric car craze by threatening to require automakers to sell large numbers of vehicles with zero emissions of hydrocarbons, which cause smog. The industry fought back and persuaded the state to loosen its requirements. California's retreat killed the prospects of electric cars among the big automakers, but created a generation of lower-emission vehicles now available nationwide.

The latest battle stems from a state law passed last year and signed by Gray Davis, who was governor at the time, calling for the California Air Resources Board to set standards that reduce cars' output of carbon dioxide. The board's staff will release its final version of the regulation next month, and the board plans to review it in September. It could go into effect by the end of 2005.

In the meantime, the auto industry has been devouring a draft version of the regulation released last month. The proposal, nearly 200 pages long, says manufacturers can achieve the reductions using currently available technologies, such as turbochargers to make smaller engines more powerful, making car bodies more aerodynamic and offering more gas-electric hybrid vehicles such as the Toyota Prius.

Carmakers say the conclusions are unrealistic. "There is a huge gap between what can feasibly be accomplished today and what the staff draft has proposed," said Dave Barthmuss, a spokesman for General Motors. "It would essentially mandate that multiple technologies be put on every California vehicle, which would dramatically increase cost and we believe dramatically reduce choice" for consumers.

And because of the size of the California marketplace, "I suspect the changes would have to be implemented on a much broader scale to make [economic] sense," Cabaniss said. "It goes to the heart of not just the engine or transmission, but the complete design of the vehicle and the materials used. It could eventually touch essentially everything about the design of a motor vehicle."

U.S.-based car companies would find it harder to meet such demands than their overseas competitors. Detroit's Big Three make virtually all their profits on the biggest, most fuel-consuming trucks and SUVs, which would be the hardest-hit by California's proposed regulation. Japanese rivals Honda and Toyota can better absorb the costs through higher overall profit margins and have a head-start on hybrid and other technologies that could help meet the stricter standards.

But Cabaniss argued that California regulators have failed to show that cutting carbon dioxide would help the environment enough to justify such drastic changes. "This is a global climate issue -- not California, and not U.S. It's clearly not going to have a great effect," Cabaniss said.

Automakers delivered similar warnings at a workshop with California Air Resources Board staffers earlier this month, which a board spokesman said was the first significant input from industry.

"The auto companies have not participated very well," board spokesman Jerry Martin said. "They have been very candid in saying they intend to file lawsuits, so they don't want to be participating in any of the rule-making process. . . . That hurt us because they are the experts at building cars. We need that interplay from them."

He said the board still hopes it can work with industry to avoid fighting the matter in court. The input from automakers at the recent workshop was "a big step forward," Martin said. "Hopefully that gridlock is beginning to break."

California wants to cut vehicular carbon dioxide emissions by 30 percent over the next decade.California air regulators want to reduce vehicular carbon dioxide emission by 30 percent over the next decade. Automakers argue the state is dreaming.