FRANKFURT (Reuters) - Germany's Daimler said on Wednesday that Mercedes-Benz trucks chief Hubertus Troska will take over a newly-created portfolio for China to boost the car maker's flagging business in the world's largest auto market.

Daimler has been struggling for some time to improve distribution networks in China, weighing on regional deliveries of Mercedes-Benz luxury cars, which fell 6.6 percent in November to 16,876 units.

By contrast, German rivals BMW and Volkswagen's Audi have long been posting double-digit gains in vehicle sales in the lucrative Chinese market, extending their global lead over Stuttgart-based Daimler.

Troska's appointment is a "long needed change at the top" of Daimler, London-based Credit Suisse analyst David Arnold wrote in a note published on Wednesday. "Daimler's China operations are one of the major disappointments for markets."

Daimler's move reflects the heightening competition among Germany's top car makers for greater business in the Asian nation. VW, the first overseas car maker to enter China three decades ago, appointed executive board member Jochem Heizmann in June to take charge of a special portfolio to oversee future expansion in China.

"We are underscoring the strategic importance of China for Daimler," Daimler Chairman Manfred Bischoff said in a statement. "We continue to see great potential there for sustained growth and the continuous expansion of our business."

(Reporting by Andreas Cremer and Edward Taylor)