LOS ANGELES -- It will take as long as 35 years for electric vehicles to gain a significant share of the global auto market, says Stefan Jacoby, CEO of Volkswagen Group of America.

The technology may be ready before then, he says, but it could take that long to reduce the cost and build the infrastructure.

"What would happen if 50 million new electric customers would plug their electric cars in an electric socket?" he asks. "There is no country on earth that is really properly prepared for electric cars."

This month, Volkswagen Group CEO Martin Winterkorn said safe and affordable electric cars for daily use are "very far away." Volkswagen has long touted diesel as the most viable fuel-efficient technology in the near term.

Already, 30 percent of the VW Jettas sold in the United States have clean diesel engines. Starting with a new, mid-sized sedan in 2011, 30 percent of the vehicles to be built at a VW factory under construction in Chattanooga, Tenn., will be clean diesels.

Jacoby discussed sustainable development with business students and reporters on Thursday at the University of California at Los Angeles.

It is unrealistic to expect the United States and Europe "and especially the emerging markets" to switch to advanced technology vehicles within a decade, Jacoby says.

Electric motor technology is "not really properly developed" in terms of safety, durability, and recycling, he says. Existing electric motors run well at high, sustained speeds, but don't work as well in low-speed city driving with frequent stops, he says.

In contrast, Toyota Motor Corp., General Motors, Ford Motor Co., Honda Motor Co., Nissan Motor Co., BMW AG, Mitsubishi Motors Corp. and Chrysler LLC have or plan to launch cars that use electric motors.

"We have to live for a certain period with fossil fuel engines," says Jacoby. "The good news is that the existing engines can be dramatically optimized" to get better mileage.

Within 10 years, fossil fuel-powered engines will get up to 70 mpg, he predicts.

Jacoby also supported a higher gasoline tax in the United States.

In Europe, diesel fuel is taxed less heavily than gasoline. That has encouraged consumers to buy more fuel-efficient, diesel-powered cars, he says.

Says Jacoby: "Out of my European experience, I think this is a good solution."

April Wortham contributed to this report