Los Angeles ? California air regulators on Friday unanimously approved the world’s most stringent rules to reduce auto emissions that contribute to global warming — a move that could affect car and truck buyers from coast to coast.

Under the regulations, the auto industry must cut exhaust from cars and light trucks by 25 percent and from larger trucks and sport utility vehicles by 18 percent. The industry will have until 2009 to begin introducing cleaner technology, and will have until 2016 to meet the new exhaust standards.

The move by the California Air Resources Board came despite vigorous opposition from auto industry officials, who argued that the board did not have the authority to adopt such sweeping regulations and that they could not be met by current technology.

The industry has threatened to challenge the regulations in court. Gov. Arnold Schwarzenegger has expressed support for the proposals and has pledged to fight any such lawsuits.

Schwarzenegger’s environmental protection secretary, Terry Tamminen, said that California should do its part to reduce pollution.

“We can make it clear that yes, we understand that our contribution, no matter how large or small, makes a difference,” Tamminen said. “Every single action that we take — or inaction — makes a difference.”

Heat-trapping greenhouse gases such as carbon dioxide and carbon monoxide are believed by many scientists to contribute to global warming.

Automakers will be required to reduce emissions by way of such innovations as better air conditioners, more efficient transmissions and smaller engines.

Automakers argued that the regulations would raise new vehicle costs as much as $3,000. But the agency’s staff said that the automakers had exaggerated and that the cost increases would top out at about $1,000 per vehicle by 2016.

Gloria J. Bergquist, a spokeswoman for the industry trade group Alliance of Automobile Manufacturers, said no decision has been made on whether to challenge the regulations in court.

Bergquist said introducing the technology would be “almost as complicated as developing the first automobile.” And she complained that the regulations would reduce worldwide emissions of greenhouse gases by only “one-tenth of 1 percent.”

“We see that as no apparent health benefit at a great cost to California consumers,” she said.

The new standards could have coast-to-coast effect: Because California represents 10 percent of the national auto market, the auto industry often overhauls all of its cars to meet California’s standards. Also, other states sometimes follow California’s lead when it comes to adopting clean-air standards.

California is the only state able to set its own vehicle pollution standards. Other states can adopt either federal vehicle pollution standards or California’s.

Board members said they were disappointed automakers did not accept invitations to work with them on the regulations.

“The response, the silence, was deafening,” said the chairman, Alan Lloyd. “I hope that we still can work together on this tremendously important issue. The stakes could not be higher.”