Porsche will only build a diesel-powered Cayenne if North Americans overcome their reluctance to buy diesel cars, said Klaus Berning, Porsche’s head of sales and marketing.

Berning said U.S. car buyers would need to switch to diesel cars in big numbers to make it economic for Porsche to launch a diesel car.

“We check the business case for diesel-powered cars every year,” Berning said in an interview. “But Porsche needs products that sell worldwide. So whether we decide to bring a diesel version or not is related to the success of diesel cars in North America because it changes the business case.”

Berning said it is not clear whether German premium carmakers will succeed in their efforts to sell diesel cars in the U.S. in large numbers.

Audi diesel for Porsche?

Many Americans think diesel cars are noisy, dirty and lacking in power.

"Only 3 percent of 16 million new cars sold in the US last year were diesels," said Ulrich Winzen, chief analyst for Polk Marketing Systems.

Mercedes-Benz, BMW, Audi and Volkswagen are trying to persuade U.S. car buyers to switch from gasoline to new clean-diesel cars, especially now that gasoline prices are rising in the U.S.

Last year, Porsche CEO Wendelin Wiedeking told Automotive News Europe that he didn’t think offering diesels would make sense because of the additional costs and relatively low sales volumes of Porsche cars. But he said Porsche continually evaluates the feasibility of adding diesel variants of one or more of its models.

A London institute called Automotive Industry Data said in a newsletter last month that Porsche will introduce a diesel-powered Cayenne by the middle of next year. The newsletter said Porsche likely would use the V6 diesel that Audi offers in its Q7 SUV.

Porsche plans to take majority control of Audi parent Volkswagen group in the next six months, raising its stake in VW to more than 50 percent from 31 percent.

Currently, Porsche has no diesel cars but plans to introduce a hybrid version of the Cayenne in 2010. It will also build a hybrid version of its new Panamera sedan.