ATLANTA - While Porsche's April sales were up 17 percent when compared with the same period in 2009, U.S. sales have grown only 3 percent. Detlev von Platen, the CEO of Porsche Cars North America, expects sales to pick up when the redesigned 2011 Cayenne and the V6 version of the Panamera go on sale later this summer.

Porsche is facing many challenges as it tries to increase sales and meet a tougher federal fuel economy target of 41 mpg by the 2016 model-year. The requirement has Porsche working hard to develop more fuel-efficient models, which is now a possibility since the company is merging with Volkswagen AG. Von Platen says that the two companies are in discussion on possible platform and technology sharing.

The new four-door Panamera was Porsche's best-selling model in the U.S. so far this year. To date, Porsche has sold 3,410 Panamera models in the U.S. since it went on sale in October 2009.

The Porsche Panamera V-6 and Porsche Panamera 4 are powered by a 3.6L V-6 engine making 300-hp and a peak torque of 295 lb.-ft. Prices start at $74,400 for the base V-6 Panamera and $78,900 for the V-6 Panamera 4.