Wagoner, speaking to the National Automobile Dealers Association convention in San Francisco, said several states want to go beyond requirements passed by Congress.

If that happens and automakers must focus on state regulations, they won't be able to focus as much on alternative fuel vehicles to reduce oil consumption and pollution, he said.

"We're not going to be able to accomplish everything that we otherwise could," Wagoner said.

EPA Administrator Stephen L. Johnson in December denied a federal waiver that would have allowed California to enact its own law slashing greenhouse gas emissions from cars and trucks.

Other states could then have followed suit and 12 were ready to do so, with others making preparations.

Because global warming is an international phenomenon not unique to California, the state doesn't need its own standards to meet "compelling and extraordinary conditions" as set out in the law, Johnson has said.

About 10,000 auto dealers and their spouses are attending the four-day NADA convention.

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