Those big S.U.V.'s and trucks rumbling down the road? With gasoline at $4, they may soon be dinosaurs.

Following production cuts by Ford Motor last month, General Motors says it will close four North American plants to reduce its output of trucks and S.U.V.'s. It will also increase capacity at some smaller car plants.

And in a decision that has much symbolic importance, G.M. says it is engaging in a "strategic review" of the Hummer—the biggest of the Big Wheels—a review that could lead to a sale.

"From the start of our North American turnaround plan in 2005, I've said that our goal is not just to return G.M. to profitability, but to structure G.M. globally for sustained profitability and growth," said Rick Wagoner, the company's chief executive.

"Since the first of this year, however, U.S. economic and market conditions have become significantly more difficult," he said. "Higher gasoline prices are changing consumer behavior, and they are significantly affecting the U.S. auto industry sales mix."

Speaking before the company's annual meeting in Wilmington, Delaware, Wagoner says high oil prices are here to stay. "We believe it is, by and large, permanent," he said.

Faced with that outlook, the company has approved funding of the Chevy Volt, an extended-range electric vehicle.

"We believe this is the biggest step yet in our industry's move away from our historic, virtually complete reliance on petroleum to power vehicles," Wagoner said.