General Motors Corp. Vice Chairman Bob Lutz said his company's new hybrid system will be able to drive on electric power alone at very low speeds.

The new powertrain, which GM plans to unveil Tuesday at the Geneva Motor Show, is an upgrade of the auto maker's current "Belt Alternator Starter," or BAS, drivetrain that is used on hybrids such as the Saturn Aura and Chevrolet Malibu.

The system is a so-called "mild" powertrain, which gets limited fuel savings because it doesn't generally drive on electric power alone. That's in contrast to the more efficient "full" system in Toyota Motor Corp.'s Prius car.

GM will upgrade its system with more powerful lithium-ion batteries. GM will call the new system "BAS-plus," according to people familiar with the company's plans. The first supply contract for the batteries will go to Japan's Hitachi Ltd., these people said.