California wants to implement a 2002 state law that would require automakers to begin making vehicles that emit fewer greenhouse gas emissions by model year 2009. It would cut emissions by about a quarter by the year 2030. But the law can take effect only if the EPA grants the state a waiver under the Clean Air Act.

"Unfortunately, the Bush administration has really had their head in the sand," Attorney General Jerry Brown said. "In this case, there has been an unreasonable delay."

The EPA held hearings this summer on California's waiver request, and administrator Steven Johnson told Congress he would make a decision by the end of the year. The schedule has not changed, EPA spokeswoman Jennifer Wood said Monday.

The agency is also crafting national standards that it will propose by the end of the year, Wood said.

Gov. Arnold Schwarzenegger in April warned the EPA he would sue if the agency failed to act on the waiver within six months. That deadline is Tuesday.

"We feel like it's a reasonable request," Schwarzenegger spokesman Aaron McLear said. "They've delayed for a long time, and it's time to take action."

Connecticut, Pennsylvania and Washington also plan to join California's lawsuit against the EPA, officials in those states said.

While the federal government sets national air pollution rules, California has unique status under the Clean Air Act to enact its own regulations — with permission from the EPA. Other states can then follow either the federal rules or California standards, if they are tougher.

Eleven other states — Connecticut, Maine, Maryland, Massachusetts, New Jersey, New York, Oregon, Pennsylvania, Rhode Island, Vermont and Washington — are ready to implement California's emissions standards if it gets the waiver. The governors of Arizona, Florida and New Mexico have said their states will adopt the standard.

The Association of International Automobile Manufacturers, which represents Honda, Nissan, Toyota and 11 other foreign car companies, has sued to block the standards from taking effect.

It argues that the tougher standards would raise the cost of cars and could force manufacturers to pull some sports utility vehicles and pickup trucks from showrooms. Their case is pending in federal court in Fresno.

The Alliance of Automobile Manufacturers has asked the EPA to deny the waiver, arguing there should be one federal standard for tailpipe emissions.