General Motors expects to start its car financing business in China by September or October, helping to boost sales in one of its fastest-growing markets, an executive reportedly said on Tuesday.

"We hope we might be operational by the end of the third quarter or the early fourth quarter," Christian Weidemann, GM China's director of financial services, told a motor industry summit in Beijing, according to Reuters.

The news agency noted that China issued rules last October to allow carmakers to offer credit to their customers, and GM said it was the first foreign car company to apply when it asked for approval in late December.

"It didn't help us really, because we are still waiting for our licence and we probably still have some time to go," Weidemann reportedly said.

"If you ask me again in a month, I will probably tell you we will get approval later," Weidemann added with a chuckle, according to the report.

Weidemann reportedly said fewer than 20% of new cars sold in China were financed, with large state banks dominating the market.

In 10 years, up to half of Chinese car buyers would be financing their purchases, but the industry still needed a national credit rating system and procedures for reclaiming cars that were defaulted on, he said, according to Reuters.

The news agency said the stakes are huge in China, where car sales nearly doubled last year, making the country the focus of foreign manufacturers seeking higher growth.

Other foreign car makers such as Toyota have also applied to set up financing arms in China, Reuters said, noting that GM on Monday said it would invest another $US3 billion in China over three years to more than double capacity.