California and seven other states are fighting a proposal by Rep. Rick Boucher, a Democrat from coal-producing southwest Virginia, that would prevent the US Environmental Protection Agency from allowing California to receive a waiver from federal rules so it could implement more stringent state requirements.

Eleven states have adopted requirements that match California's and six others are considering it, said BreAnda Northcutt, spokeswoman for the California Environmental Protection Agency.

If the EPA grants California's waiver, the other states would be free to implement similar emissions-cutting standards.

Seven states say they want to follow California in requiring that cars and light trucks reduce climate-changing greenhouse gas emissions -- primarily carbon dioxide -- by 18 percent by 2020.

"We urge you to pursue legislation that instead enhances and complements the efforts already under way in our states," the eight governors said in a joint letter to Boucher.

"This bill," the governors said, "will pre-empt California's passenger vehicles and light duty truck emission standards."

The eight states signing the letter were California, New York, Pennsylvania, Massachusetts, Washington, Arizona, Oregon, and New Mexico.

The governors said the bill would deny not only states' rights to adopt California's vehicle emissions standards, a right granted by the federal Clean Air Act, but would also eliminate the EPA's regulatory authority over greenhouse gases as a pollutant.

"This amounts to an about-face reversal of the Supreme Court decision identifying CO2 as a pollutant within the scope of the Clean Air Act," they said.

The 11 states that have adopted California's strict requirements are New York, Pennsylvania, New Jersey, Massachusetts, Washington, Maryland, Oregon, Connecticut, Maine, Rhode Island and Vermont, according to the California Energy Commission.