The Washington, D.C.-based Alliance of Automobile Manufacturers, representing Detroit and foreign automakers, said it joined with a group of California car dealers in filing a lawsuit in US District Court in Fresno, California, on Tuesday challenging the rules.

The suit challenges California's legal authority to regulate motor vehicle fuel economy, the industry group said.

"Federal law is designed to ensure a consistent fuel economy program across the country," Fred Webber, president and chief executive of the Alliance, said in a statement.

"There's a better way to improve fuel economy than this regulation, such as providing consumer tax incentives for the purchase of our new advanced technology vehicles," Webber said.

The National Highway Traffic Safety Administration has sole authority under federal law to set a uniform national fuel economy standard, according to the automakers.

The Alliance members are Ford Motor Co. General Motors Corp. DaimlerChrysler and six other car and truck companies.

The emission rules for California, the nation's biggest auto market, will require automakers to cut emissions in cars and trucks by as much as 25 percent beginning with the 2009 model year, with cuts accelerating to about 30 percent in 2016.

HIGHER PRICES?

The standards will raise car prices in California by an average $3,000, the automakers said, but proponents of the regulations said the claim was exaggerated.

New York, New Jersey and the New England states have said they are likely to follow the California rules when making their own plans to reduce vehicle pollution, and Canada is studying the program.

California and New York state officials promised Tuesday to enlist their huge pension funds to pressure the auto industry to comply with the emission rules.

California Controller Steve Westley and Alan Hevesi, New York comptroller, said in a teleconference they will work to persuade Detroit to recognize the need for cleaner air.

"We want the companies to move in the right direction," Hevesi said.

Westley said the state pension funds "put pressure on corporate America to do the right thing," with proxy fights "a last resort."

Employee and teacher pension funds in the two states have more than $2 billion invested in automakers, he said.

Calpers, the nation's biggest pension fund, is expected to ask automakers to come to Sacramento to explain their opposition to the emission regulations, Westley said.

"California has long had the right to regulate air pollution and the automakers are trying to stand in the way," said Louise Bedsworth, senior analyst for the Union of Concerned Scientists, an activist group that issued a report Tuesday on pollution performance of vehicles produced by the six largest automakers in the US market.