TRAVERSE CITY, Mich. – General Motors Corp said Thursday it would finalize the design of the all-electric Chevy Volt by mid-September and aims to have 50 prototypes with production-ready parts by the end of 2008.

GM has been racing to finish development of the Volt in time for its planned launch in 2010. The Volt is the centerpiece of GM's effort to move away from large SUVs, as truck sales tumble and gasoline prices remain high.

“We have one gate in our process we call a styling freeze, which is happening in the middle of September,” Frank Weber, GM's vehicle line executive in charge of the Volt, told reporters on the sidelines of an automotive conference.

Bob Boniface, GM director of design for the Chevy Volt, showed a few sketches of the front end of the final design at the automotive conference.

Boniface said the front edges of the production model are more rounded compared with the concept version, which GM disclosed in January 2007 but has since retooled to improve the aerodynamics.

GM is designing the Volt to run for 40 miles (64 kilometers) on a lithium-ion battery pack that can be recharged at a standard electric outlet.

Weber said a few prototypes with production-ready parts would be ready in the next 10 days.

While both Weber and Boniface are confident the Volt can deliver the automaker's targeted gasoline-free range, the introduction of thousands of electric vehicles still depends on advances in lithium-ion battery technology and the ability to bring down the cost of the vehicle.

“The No. 1 priority is to make the battery program robust,” Weber said. “The conceptual future is not to extend the range much further.... The future is to take the same range and the same original 40 miles but then have battery packs about half the size, twice the robustness and half the cost.”

GM, which has already featured the Volt in its advertising as part of a bid to improve its public image, is planning an initial volume of 10,000 vehicles.

Weber said GM intends the Volt to be a mass-market vehicle.

“We've always said the Volt is not a niche program,” he said. “Niche volume would not work. All the suppliers are looking for significant volumes to build up capacity and make sure this also works for them.”

(Editing by Gerald E. McCormick and Derek Caney)