General Motors Co. will build a pure-electric vehicle by expanding the Chevrolet Volt’s battery pack and removing its internal combustion engine, Vice Chairman Bob Lutz said Monday.

It’s the next step for the Volt, a car the company says can run 40 miles on a charge from a standard home power outlet. After the battery wears down, a 1.4-liter four-cylinder internal combustion engine takes over and generates electricity to power the car.

It’s due to go on sale this fall at a cost of about $40,000, before tax credits.

Lutz would not say exactly when the pure-electric version would make it into showrooms, but said it would be “technologically trivial” to switch out the internal combustion engine.

Lutz told reporters at the Detroit auto show that GM could quickly expand the Volt’s battery pack and take out the engine to build a fully electric car similar to Nissan’s Leaf.

The Leaf, also to go on sale in the U.S. late this year, can get up to 100 miles on an electric charge but must be recharged or have a new battery installed to go any further. More