General Motors Co will produce its next-generation electric cars in South Korea, the head of its South Korean unit told Reuters on Thursday, as the US carmaker tries to revive momentum for the stalling vehicle technology.

Sergio Rocha, CEO of GM Korea, gave no time frame for the launch of the new vehicles, but said they would be slightly bigger than the Spark small car and use a thoroughly new design, unlike the Spark EV which was based on an existing gasoline engine model.

GM will continue working with South Korea's LG Chem Ltd to supply batteries for its second generation of electric vehicles, which will be produced at GM's plant in Bupyeong, near Seoul, he added.

"This (next-generation electric) car has a lot of similarities with the products we produce today in Bupyeong," Rocha said in the interview, on the sidelines of the Seoul auto show.

GM Korea, which makes more than 40 percent of GM's Chevrolet-branded vehicles and specializes in developing small cars for the US company, produces the Aveo, Trax, Captiva and Malibu at its Bupyeong plant.

Electric vehicles such as GM's Volt and Nissan Motor Co's Leaf are struggling to gain traction, hobbled by limited driving range, a lack of charging infrastructure and high prices.

GM Chief Executive Dan Akerson said early this month that the US automaker was developing new EVs, including one with a 100-mile range and another with a 200-mile range.

GM Korea started production of its current generation of Spark EVs in Korea this month for export to the US. market and plans to begin selling it in South Korea and Europe in the second half of the year.

LG Chem makes the lithium-ion batteries for GM's electric vehicles, which are produced in Korea and the United States.