California air regulators on Thursday gutted rules seeking to place tens of thousands of zero-emission vehicles on the road but instead forced automakers to produce a fleet of cleaner-burning hybrids.

The decision is expected to affect 12 other states that had adopted California's target for zero-emission vehicles, defined as those powered solely by batteries or hydrogen fuel cells.

The California Air Resources Board voted to lower by 70 percent the number of zero-emission vehicles automakers must sell here and in the states that intended to follow California's lead.

Instead, the air board said the six largest automakers must sell nearly 60,000 plug-in hybrid vehicles in California while they develop the more advanced technology that will allow mass production of pure zero-emission vehicles.

Board chairwoman Mary Nichols described the move as a major step toward putting cleaner cars on the road. The plug-in hybrids envisioned by the air board have yet to be produced but are in development by several automakers.

"We're introducing a whole new category of vehicles to the public," Nichols said. "I don't think it's a step backwards in the real world."

In essence, the air board took two steps on Thursday: It cut the number of zero-emission vehicles it wants on the road by 2014, while at the same time offering an alternative -- the gas-electric hybrids.

Environmentalists and health advocates criticized the lowering of the zero-emission goal for vehicles. They said the threats posed by global warming, combined with rising gasoline prices, lends urgency to greatly reducing vehicle emissions.

"We are disappointed. We think this proposal doesn't take us on the road to meeting the state's long-term global warming goals," said Spencer Quong, a senior vehicles analyst at the Union of Concerned Scientist.

Auto manufacturers said they could not meet the California standard and needed more time to make affordable hydrogen- and battery-powered cars.

"Pushing this technology into the market before they are commercially viable ties up resources that could be better utilized by advancing core technologies," said Sara Rudy, an emissions regulatory manager at Ford Motor Co. "It is important at this stage to be nimble."

The other manufacturers that must comply with the rules are General Motors Corp., Toyota Motor Corp., Honda Motor Co., Chrysler LLC and Nissan Motor Co.

General Motors is developing a rechargeable vehicle it hopes to have on the market in 2010. The Chevy Volt would run on a battery for 40 miles, and then fuel would power the onboard generator, GM spokesman Dave Barthmuss said.

Automakers praised the air board's decision to promote the plug-in hybrids over the zero-emission vehicles. For example, they said California and other states lack the fueling stations to support hydrogen vehicles.

Gov. Arnold Schwarzenegger has promoted placing hydrogen stations along California's interstates, but only a handful exist. On Thursday, the air board indicated that it might someday require oil companies to build those stations.

"I think we ought to consider infrastructure a requirement on fuel providers," air board member Dorene D'Adamo said. "It's about time they participate in this program."

California adopted its zero-emission vehicle mandate in 1990 as part of an attempt to reduce smog-forming emissions such as nitrogen oxide.

The rule required that 10 percent of new cars sold in the state by the country's six leading auto manufacturers be completely nonpolluting by 2003.

The rules have been modified four times since they were introduced. The biggest change came in 2003, when the Air Resources Board significantly scaled back the mandate and ruled that hydrogen cars, hybrids and cleaner-burning gasoline vehicles could meet the state's goals.

The regulators were concerned that battery-powered cars could not be mass-produced and favored hydrogen cars. They also faced a lawsuit from the auto industry.

Although some lower-emission vehicles -- especially hybrids -- have begun making an impression in the marketplace, the main automakers still do not have a commercial zero-emission vehicle.

The revised 2003 rules set a goal of putting at least 25,000 zero-emission cars on the road in California by 2014, far below the original 10 percent mandate.

The rules adopted Thursday put the number of zero-emission vehicles required nationwide by 2014 at 7,500, a 70 percent reduction from the 2003 target.

Automakers will be allowed to sell those vehicles in California and the 12 other states. Critics wanted all 7,500 to be sold in California, with additional zero-emission cars sold elsewhere.

The 12 other states that adopted the California standard are Connecticut, Maine, Maryland, Massachusetts, New Mexico, New York, New Jersey, Oregon, Pennsylvania, Rhode Island, Vermont and Washington. Automakers are required to sell 120,000 of the new plug-in-hybrids in those states by 2014, said Tom Cackette, the air board's chief deputy executive officer.

Arizona, Colorado, Florida and Utah are considering California's standard, according to the Air Resources Board.

California is the only state allowed to go beyond federal law in setting such environmental standards, but other states can follow its lead.

The changes adopted by the air board will affect just a fraction of the overall fleet in California. About 1.5 million new vehicles are sold in the state each year.

Despite California reducing its target for zero-emission vehicles, some environmentalists said Thursday's action will force the auto industry to change its thinking.

"For the first time, the automakers have a requirement to put tens of thousands of plug-in-hybrids to the showrooms," said Luke Tonachel, a vehicle analyst at the Natural Resources Defense Council.

The air board also asked its staff to study an overhaul of the zero-emission program because it fails to take into account how many clean-running cars are needed to meet the state's global warming goals. Those goals were set by a 2006 law that requires a massive reduction in greenhouse gas emissions statewide.