The House of Delegates overwhelmingly approved legislation yesterday that could make Maryland the 12th state to force carmakers to slash emissions thought to cause global warming.

Senate leaders predicted approval of a similar bill this week, and Gov. Martin O'Malley (D) has pledged to sign the legislation.

The stricter standards for cars and trucks hitting dealerships in 2010 would put Maryland in the forefront of states seeking to slow climate change, environmentalists said. But automakers said the requirements would raise prices and reduce choices for consumers -- to make way for more fuel-efficient cars, fewer sport-utility and other large vehicles would be on the market.

Because the best way to reduce gases is to use less fuel, the legislation would require vehicles to be more fuel efficient. The law is designed to raise the state's average fuel efficiency for new vehicles sold in Maryland to 43 miles per gallon. The current average for light trucks and SUVs is 22.2 mpg and for cars, 27.5 mpg.

Five years ago, California became the first state to regulate emissions of carbon dioxide from car tailpipes. The higher standards are to take effect in 2009, but the auto industry has sued that state to block them.

Maryland lawmakers -- mindful of cancer rates, asthma and rising water levels hastened by climate change in the Chesapeake Bay -- are pushing a slew of clean-energy initiatives this session.

"It's a big day," House Speaker Michael E. Busch (D-Anne Arundel) said, estimating that the Clean Cars Act would take the equivalent of 190,000 vehicles a year off the road. "People for years wrote off climate change. Now they're seeing things like Hurricane Katrina, tsunamis, and they know the causes of melting ice caps have credibility."

The 122 to 16 House vote included Republican support and reflected the power of the state's environmental movement after passage of legislation last year to curb pollution from coal-fired power plants. O'Malley highlighted clean cars in his State of the State speech last month and embraced the measure in his first-session legislative package.

"He thinks we have a responsibility to lead the fight against global warming," spokesman Rick Abbruzzese said.

New cars in Maryland with 7,500 or fewer miles would have to be built to emit about a third less carbon dioxide from the mix of cars sold in Maryland than today's models. Emissions of other pollutants, including carcinogens and nitrogen compounds that foul the bay, would also be cut.

A percentage of the cars on dealers' lots would have to be manufactured like hybrids, with advanced technology, including some with zero emissions. Motorists would not need to retrofit their cars, but they could not bypass the rules by buying cars in another state: They would be blocked from registering those in Maryland based on their vehicle identification numbers.

The carbon dioxide rule, aimed at reducing emissions of gases produced by burning coal, oil and gas, met the stiffest resistance from automakers.

Carmakers estimate $3,000 would be added to consumers' costs. And they argue that by adopting California's emissions standards, Maryland, New York, New Jersey and other states are ceding their power if California should decide to tweak its regulations.

"This legislation will result in higher costs, reduce choices and give California the authority to make decisions about the vehicles Marylanders drive," said Charles Territo, spokesman for the Alliance of Automobile Manufacturers, which lobbied heavily against the bill.

"Some of us are a little uncomfortable with that," said House Minority Leader Anthony J. O'Donnell (R-Calvert), who voted against the measure.

Territo disputed any health or environmental benefits from reducing carbon dioxide emissions.

The carbon dioxide rules have not taken effect in other states, so there is no test case yet for Maryland consumers.

But environmental groups said the carbon dioxide rules can be met through current technology. Advocates said that average car prices would rise about $1,064 but that in the long term, cleaner cars would save money.

The auto industry blocked the clean cars bill for three years. "General Motors came in and said, 'We have a plant here in Maryland. You'll have to close that plant,' " recalled Del. Maggie McIntosh (D-Baltimore), chairwoman of the House Environmental Matters Committee. Said Del. Elizabeth Bobo (D-Howard), sponsor of the House bill: "We didn't pass the bill, and they still left," closing the GM plant in Baltimore. GM's waning influence in the state and a "lot of education about air and air quality" pushed the measure forward this year, McIntosh said.

The General Assembly is considering other anti-pollution and energy efficiency measures, including bills to reward greater reliance on solar and wind-powered energy. Another bill would revive a tax break for hybrid cars.