NEW YORK (CNNMoney.com) -- General Motors announced plans Tuesday to shut four truck and SUV plants that employ thousands of workers. It also said high gas prices are here to stay - and, with them, consumers' growing preference for more fuel-efficient vehicles.

At a news conference in Wilmington, Del., GM Chairman and CEO Rick Wagoner announced plans to roll out more fuel-efficient vehicles, including approval to start the production process on a vehicle that can run gas-free for trips up to 40 miles.

But the plant-closing plans are a stunning admission from the nation's largest automaker that its long dependence on large SUVs and pickups is no longer a viable strategy for a company struggling to end losses from its North American operations.

The plants to be closed include two U.S. facilities: The Moraine, Ohio plant that builds midsize SUVs, such as the Chevrolet Trailblazer and GMC Envoy; and the Janesville, Wisc., assembly line that builds large SUVs such as the Chevy Tahoe and Suburban and GMC Yukon.

In addition, it plans to close a pickup plant in Oshawa, Canada, and a truck plant in Toluca, Mexico.

The Mexican plant that builds medium-duty trucks sold to businesses rather than consumers will close later this year. The other plants will close in 2009 and 2010, with sooner closings possible if sales do not improve. Each U.S. plant has about 2,500 employees.

The company said it believes that high oil and gasoline prices will be the norm, and that prices are likely to go higher due to strong global demand for oil.

"These higher gasoline prices are changing consumer behavior and rapidly," said Wagoner. "We don't think this is a temporary spike or shift. We think it is permanent."

Goodbye Hummer Wagoner also said GM is looking at possibly selling its Hummer unit as part of a strategic review of the SUV brand based on military vehicles. The Hummer H3 mid-size SUV gets about 13 to 14 miles per gallon in city driving in the most recent EPA ratings. The H1 and H2 are larger vehicles on which EPA does not give mileage estimates.

The brand has become the symbol to many members of the public of a gas-guzzling large U.S. vehicle.

Hello Volt He also announced that GM has approved production of the Chevrolet Volt, a so-called plug-in hybrid vehicle that can run about 40 miles without any use of gasoline. The Volt will be built in GM's Hamtramck, Mich., plant and is due in showrooms by the end of 2010.

"We believe it's the biggest step yet in our industry's move away from its historic, nearly complete reliance upon petroleum to power vehicles," he said. "We believe the Volt is an important investment for the future of our company and our shareholders."

Ahead of the rollout of that new model, GM plans to increase production of some more fuel-efficient car models. It's adding a third shift at its Orion, Mich., plant to build more of the Chevy Malibu and Pontiac G6 models, as well as a third shift at a Lordstown, Ohio, plant that builds the compact Chevrolet Cobalt and Pontiac G5 models.

It also plans a more fuel-efficient gasoline engine for its small car models that will get about 9 miles per gallon more than current GM engines in the segment.

The plans were announced ahead of GM's (GM, Fortune 500) annual meeting Tuesday in Wilmington. They followed similar plans unveiled last month by rival Ford Motor (F, Fortune 500), although Ford did not give details of plant closing plans.

About 19,000 U.S. hourly employees had already agreed to take buyout and retirement bonuses to leave the company in recent months, but it had originally planned to replace most of those workers with lower-wage new hires who were not due the same expensive benefit package.