WASHINGTON — Backed by dozens of environmental groups and other states, top California officials demanded federal permission Tuesday to impose controls on greenhouse gas emissions from cars and other vehicles.

WASHINGTON — Backed by dozens of environmental groups and other states, top California officials demanded federal permission Tuesday to impose controls on greenhouse gas emissions from cars and other vehicles.

The lone voice of opposition at an Environmental Protection Agency hearing came from an auto industry lobbyist who deemed California's approach "counterproductive" and said there was no proof it would help reduce global warming.

"This is more important than any issue that EPA's going to have to face," California Attorney General Jerry Brown told regulators who will recommend whether to give California the waiver it needs to implement its tailpipe emissions law.

At least 11 other states are ready to follow California.

Brown asked the hearing panel to take a message to EPA Administrator Stephen Johnson.

"We want him to speak truth to power," said Brown. "There is a tremendous influence of the oil industry. We know (Vice President) Cheney and (President) Bush are oilmen, they think like oil folks. ... We say grant the waiver."

At issue is a 2002 California law that requires automakers to cut emissions by 25 percent from cars and light trucks and 18 percent from sport utility vehicles starting with the 2009 model year.

California officials estimate this would lead to an 18 percent reduction in global warming emissions from cars in the state by 2020. But the law can't take effect unless California gets a federal waiver.

While the federal government has authority to make air pollution rules, California has unique status under the Clean Air Act to enact its own regulations as long as it receives permission from the EPA. Other states can then follow the federal or California standards.

Connecticut, Maine, Maryland, Massachusetts, New Jersey, New York, Oregon, Pennsylvania, Rhode Island, Vermont and Washington are ready to implement California's emissions standards, according to California officials. Six other states are actively considering them: Arizona, Colorado, Illinois, New Hampshire, New Mexico and North Carolina.

Tuesday's hearing in suburban Arlington, Va., came after more than a year of inaction since California submitted its waiver petition in 2005. During a break, Margo Oge, director of EPA's office of transportation and air quality, said it was premature to say anything about what the agency might do.

Another hearing is scheduled May 30 in Sacramento. The agency has no deadline, but Gov. Arnold Schwarzenegger has announced plans to sue if the EPA does not act on the state's request by Oct. 25.

Tuesday's session included witnesses from environmental and public health groups, as well as officials from Illinois, New Jersey, Rhode Island and Maryland, speaking in favor of California's law. The lone voice of opposition came from Steve Douglas of the Alliance of Automobile Manufacturers.

"A patchwork of state-level fuel-economy regulations as is now proposed by California is not simply unnecessary — it's patently counterproductive," Douglas said.

The state's waiver request "contains many assumptions and undocumented claims," he said.

California officials acknowledged their law won't make an appreciable dent in global warming but said it's imperative to start somewhere.

Later Tuesday, California Democratic Sen. Barbara Boxer chaired a hearing on the issue before the Senate Environment and Public Works Committee.

The committee's top Republican and leading global warming skeptic, Sen. James Inhofe of Oklahoma, ridiculed California's demand for an immediate decision on the waiver as "simply grandstanding."

"Nobody in my state is grandstanding. They're trying to step up to the challenge of global warming," Boxer responded.

The auto industry has sued California and Vermont in an attempt to block the regulation, arguing that emissions standards are de-facto fuel economy standards that can be set only by the federal government.

The auto regulations are a key part of California's overall strategy to reduce greenhouse gas emissions, which scientists blame for the Earth's warming temperature over the last three decades. The state is the world's 12th largest producer of greenhouse gas emissions, 40 percent of which come from transportation sources.

President Bush, who has opposed mandatory emissions controls, last week signed an executive order giving federal agencies until the end of 2008 to continue studying the threat of greenhouse gas emissions and what to do about them. Critics fear the directive could undermine state efforts.