"It has definitely not lived up to our original plans," Zetsche said in an interview. "We are in the early phase of thinking about the next concept. It might be a one-for-one successor to the R class or it could be different."

Mercedes-Benz initially planned annual production of 50,000 for the R class, with 25,000 vehicles slated for the US. The vehicle has never approached that volume.

In the US, Mercedes tried to increase sales by lowering the price by $5,000 and offering a three-seat second row, for a total of seven seats. Last year, R class sales in its main market, the US, fell 28 percent to 18,168 units.

"Our expectations were higher than the return," he said. "It was a lesson learned. There is a volume out there. Whatever we do in the future, it must be feasible."