DETROIT ? In one of the clearest signs yet that hybrid cars may be going mainstream, General Motors Corp. plans to offer a variety of the gas-and-electric powered vehicles during the next four years.

The plan by the world’s biggest automaker, to be announced today, includes hybrid models for cars, pickups and sport utility vehicles.

GM’s new strategy sends a clear signal that auto executives are starting to consider energy-efficient hybrids as potentially viable offerings to the mainstream motoring public.

Hybrids draw power from two different energy sources, typically a gas or diesel engine combined with an electric motor. While environmentally friendly and fuel efficient, their high cost has prevented them from finding more than a niche market.

For now, the only versions available in the United States are small cars made by Honda Motor Co. and Toyota Motor Corp.

GM will offer hybrid options on several vehicles, starting later this year with the GMC Sierra and Chevrolet Silverado pickups for use in commercial fleets. The hybrid versions of the trucks will increase fuel economy by 10 percent to 12 percent, the company says.

Those same trucks will be available to retail consumers in 2004.

Ford Motor Co. and DaimlerChrysler AG’s Chrysler Group also are planning hybrid models.