DETROIT -- Citing poor sales, General Motors will limit Chevrolet Malibu Hybrid sales to fleets while it completes development of a two-mode hybrid system that offers better fuel economy.

That two-mode hybrid powertrain is expected in about a year. The system is expected to be similar to the one used by such vehicles as the Ford Fusion and Toyota Camry.

GM reports only total Malibu sales and will not break out Hybrid totals. But the National Renewable Energy Laboratory, an arm of the U.S. Department of Energy, estimates that GM sold about 3,800 from the time the vehicle went on sale in April 2008 through April of this year.

"We have a significant inventory of 2009 [Malibu] Hybrids on dealer lots right now," said Chevrolet spokesman Steve Janisse. "We have suspended retail production of the 2010. We are producing some fleet vehicles.".

The 2009 Malibu Hybrid is a light hybrid and falls short of the fuel economy offered, for example, by the 2010 Fusion, which went on sale in April. The Malibu Hybrid is limited to such functions as:

• Shutting off the engine when the vehicle is stopped to minimize idling, then restarting the engine when the brake pedal is released.

• Using the motor/generator to bolster the gasoline engine at wide-open throttle, such as during acceleration or a passing maneuver.

• Enabling early fuel shut-off during vehicle deceleration.

The two-mode hybrid system available on the Ford Fusion propels the wheels by an electric motor, gasoline engine, or a combination of both, boosting fuel economy.

The 2010 Fusion's two-mode hybrid is priced at $27,995 including shipping, and is rated at 41 mpg city and 36 mpg highway. By comparison, the 2009 Malibu Hybrid, priced at $26,275, is rated at 26 mpg city and 34 mpg highway.

The base Malibu has a much lower sticker of $22,325, and its fuel economy isn't far behind the hybrid version. The base 2009 Malibu with the standard four-cylinder powertrain and four-speed automatic transmission gets 22 mpg city and 30 mpg highway.