Ernst Lieb has left his post as CEO of Mercedes-Benz USA after five years in the position.
He will be succeeded "until further notice" by Herbert Werner, the U.S. subsidiary's CFO and vice president for finance and information technology, Mercedes said in a statement Monday.
Daimler gave no reasons for the changes.
Mercedes canceled this week's U.S. national dealer meeting -- the Mercedes Benz Dealer Business Forum -- scheduled for Tuesday and Wednesday in Chicago.
Lieb, a 56-year-old German, had held the position since September 2006. Before that, he was head of DaimlerChrysler Australia/Pacific and previously served as CEO of Mercedes Canada.
The United States is Mercedes' second-biggest market behind Germany.
Mercedes is battling its German rivals for the titles of top-selling luxury brand in the United States and the world.
Mercedes' U.S. sales are up 7 percent this year to 170,058 units, behind BMW with sales of 177,679. The Mercedes figures exclude sales of the Sprinter van.
Toyota Motor Corp.'s Lexus brand, which has been the luxury sales leader for the past 11 years, has fallen behind with sales of 135,647, largely because of inventory shortages caused by the March earthquake in Japan.
Like other luxury automakers under pressure to meet tougher government fuel economy rules and changing consumer preferences, Mercedes is gearing up to add volume and enter new segments. A new family of front-wheel-drive compact cars arrives in 2013.
The brand wants to expand into segments below its E and S-class large vehicles to target younger buyers.
Last month, Mercedes launched its first C-class coupe to challenge the BMW 3 series' domination of the luxury compact market. Lieb was a strong proponent of the project, saying Mercedes needed more C class derivatives to better compete with its arch rival.
Mercedes plans to introduce at least 10 new models by 2020 to reclaim the title of world's top-selling luxury brand.
BMW, with 2011 global sales of 1.02 million through September, leads Audi, with sales of 973,200, and Mercedes, with year-to-date sales of 919,288 worldwide.
Under Lieb's leadership, about 300 of Mercedes' 355 U.S. dealerships have spent a combined $1.4 billion since 2008 to comply with the automaker's Autohaus design standard.
Earlier this year, Mercedes opened a revamped and company-owned Mercedes-Benz Manhattan dealership in New York City at a cost of $220 million.
Lieb was a driving force behind the project, saying Mercedes needed a powerful presence in New York. He said the automaker needed to build a new Manhattan store to the Autohaus standards that other dealers were asked to meet.
The automaker also just signed a 10-year agreement for the naming rights to the Louisiana Superdome for a reported $50 million to $60 million.
Lieb was on hand for the Oct. 4 announcement in New Orleans and it marked one of his last public appearances.
Reuters contributed to this report