Vermont, with a record of environmental measures and known for its rural beauty, is one of nine states to have followed California's lead in adopting standards that are tougher than federal rules.

The 10 states want a 30 percent cut in the amount of carbon dioxide emitted by cars, starting with 2009 models.

The United States is the world's largest source of greenhouse gases, which are blamed for raising global temperatures and changing weather patterns.

Automakers have also sued California and Rhode Island, but the Vermont case starting on Tuesday at the US District Court in Burlington is the first to go to trial.

General Motors Corp., the world's largest automaker, DaimlerChrysler AG, four local car dealerships and auto-industry trade groups filed suit in 2005.

They contend that states are overreaching their authority in trying to regulate vehicle emissions. Emissions are closely linked to fuel consumption, which is regulated by the federal government.

"This trial is about whether or not states have the authority to set their own fuel-economy standards. And we will argue that they don't," said Charles Territo, a spokesman for the Alliance of Automobile Manufacturers, a Washington-based trade group that is one of the plaintiffs.

"There needs to be a comprehensive multi-sector strategy at the federal level to effectively deal with this issue."

GOING THEIR OWN WAY

The Bush administration -- which in 2001 pulled out of the Kyoto Protocol, the main plan by the United Nations to limit greenhouse gases -- has said it plans to tackle carbon dioxide emissions on its own rather than support global caps.

The US auto industry, a powerful lobby group, says the stricter emission standards will hurt auto retailers and manufacturers, limit the availability of light trucks and provide limited environmental benefits.

Environmental advocates say that if the stricter rules are adopted by the states, it would cut emissions from new cars in about one-third of the US market.

California, one of the first states to embrace car culture, faced severe problems with smog caused by auto exhaust.

Because of its early efforts to fight pollution, US environmental laws have allowed the West Coast state to set stricter automobile pollution rules. Other states have the option of adopting the California-style standards.

"California has a long history as an innovator and can in fact generate its own emissions standards that are more stringent than those that EPA might promulgate," said Melissa Hoffer, a senior attorney at the Conservation Law Foundation, which is supporting Vermont in the case.

Vermont was the first state to adopt the California rules. The others are Connecticut, Maine, Massachusetts, New Jersey, New York, Oregon, Rhode Island and Washington.