AS China's vehicle sales more than doubled to a record high in January, extending its lead against the United States as the world's largest auto market, experts cautioned the market might overheat and the booming sales may not be sustained for the full year.

Car makers sold 1.66 million vehicles in China last month, a jump of 124 percent from a year earlier, the China Association of Automobile Manufacturers said yesterday.

Apart from a low comparative base, CAAM said a recovering macro-economy and the government's continued stimulus measures, including a lower tax for small cars and subsidies for rural purchase, bolstered the robust sales.

In contrast, January sales in the US rose 6 percent to 698,990 units.

Despite the rosy sales in January, CAAM warned they could not be sustained for 2010 on lingering concerns of economic uncertainty. But CAAM kept its full year forecast of 15 million units in sales.

An independent auto analyst Jia Xinguang also indicated that the sales momentum might be slowed.

"A lot of deliveries in January were generated by orders last year, and new orders have been dropping," said Jia.

"The supply is also quite tight, restraining growth further."

CAAM said demand in January was strong in all segments, including sales of 1.31 million passenger vehicles, a rise of 110 percent on an annual basis, and 348,200 commercial vehicles, a 180 percent jump.

Despite a smaller tax break compared with last year, sales of small cars were stable with 941,000 units sold in January, up 25 percent from December.

General Motors' Chinese sales in January soared 97 percent from a year ago to a high of 219,192 units.