General Motors Corp. will close or cut back production at 12 North American facilities by 2008 and lay off 30,000 workers, 5,000 more than previously announced, in an effort to bring auto production in line with demand, the company's chief executive announced today.

GM Chief Executive G. Richard Wagoner Jr. said at a news conference in Detroit that the world's largest automaker will be cutting the number of vehicles it produces every year by 1 million in an attempt to reduce costs by $7 billion.

Wagoner announced in early June that the company would lay off 25,000 workers. He upped that figure by 5,000 today and announced the names of the plants that would be closed or where production would be cut back.

"The decisions we are announcing today were very difficult to reach because of their impact on our employees and the communities where we live and work," Wagoner said. "But these actions are necessary for GM to get its costs in line with our major global competitors. We'll work our hardest to mitigate that impact."

The facilities to be closed include assembly plants in Oklahoma City; Lansing, Mich.; Spring Hill, Tenn.; Doraville, Ga.; and Ontario, Canada. Production will be decreased at another GM plant in Ontario and at one in Moraine, Ohio.

An engine facility in Flint, Mich., will close, along with a separate powertrain facility in Ontario and metal centers in Lansing and Pittsburgh. GM will also close three service-and-parts operations facilities -- in Ypsilanti, Mich.; Portland, Ore.; and an unidentified site.

Wagoner said earlier this year he planned to cut manufacturing capacity to match demand by 2008. The job cuts announced today represent 9 percent of the company's total work force.

"It's a big move that we've made," Wagoner said today. "We're confident that this is what it's going to take to get us going." He said the actions were necessary for GM to "get its costs in line with our major global competitors. In short, they are an essential part of our plan to return our North American operations to profitability as soon as possible."

The plant closings are not expected to be final until the company's current contract with the United Auto Workers expires in 2007.

GM stock rose on the announcement, but fell as the day progressed. It closed down 47 cents, losing about 2 percent of its value. The auto giant lost nearly $4 billion this year and its stock had lost more than 40 percent of its value, plummeting to a 14-year low last week.

The announcement underscores the dire condition of the U.S. auto industry. GM once dominated the industry, accounting for half of the new cars and trucks sold in the United States, but its market share has steadily slid during the past 30 years in the face of aggressive foreign competition.

Ford Motor Co. announced last month a $1.2 billion third-quarter loss in its core North American division and warned that it, too, would begin another major overhaul in January with "top-to-bottom" job cuts and "significant" plant closings. Analysts say Ford's condition is not as bad as GM's, which has lost money in each quarter this year.

GM has been hit by high labor, pension, health care and material costs at the same time that demand has slumped for sport utility vehicles -- the industry's cash cow -- and by bloated plant capacity. Executives at Ford and GM said the collapse of the market for SUVs has hastened the pace of the industry's revamping.

Last month, GM and the United Auto Workers announced they had reached an agreement to pare health care benefits for its workers. Wagoner has said that high labor costs were crippling the auto giant.

GM also announced it is stepping up development of more fuel-efficient technology and the rollout of hybrid-powered cars. The automaker had long relied on the popularity -- and profitability -- of its trucks and SUVs, but the run-up in gas prices has turned the strategy into a liability. Wagoner told GM employees recently that the company had "too much reliance" on trucks and SUVs.