While General Motor is struggling in US, its joint venture in Shanghai has sold its two millionth Buick in China as sales have grown rapidly, the auto giant said on Tuesday.

It took eight years for Shanghai GM to sell its first one million Buicks, but only three years to sell its second one million units, said Kevin Wale, President of GM China, in a statement.

This demonstrates the ongoing popularity of Shanghai GM's leading mainstream brand in what is now Buick's largest market, he added.

The two millionth unit, a red New Regal sedan built by a joint venture with China's largest automaker Shanghai Automotive Industry Group, was delivered to its owner in the southern city of Guangzhou, the statement said.

GM's first Shanghai sales office opened in 1929, boasting Buick owners are mostly the leading men in China. Indeed, Pu Yi, the last emperor, revolutionary leader Sun Yat-sen and premier Zhou Enlai all owned Buicks.

But that history is barely known, allowing GM to recast Buick as a car for China's young and fast-growing middle class.

Despite its US parent filing for bankruptcy, GM China has seen sales hit new highs on strong demand from the nation's increasingly affluent middle class and incentives to stimulate domestic consumption.

China overtook the United States to become the world's largest car market for the first time this January.

GM car sales in China are set to surpass those in the United States this year in a landmark shift, said Fritz Henderson, GM’s chief executive.

GM sales in China jumped 75.2% in May from a year earlier to a record monthly high of 156,000, ranking No. 1 among the Chinese car manufacturers. In the first five months, sales grew 33.8% from the same period a year ago to more than 670,000.

While GM pares back at home, it may add a plant in China to meet its goal of doubling annual sales to two million within five years with products developed for the most important growth market in the world, Wale said.

GM China has covered over 90% of city network in China.