SAN DIEGO - Hyundai posted a 45 percent gain in November sales to 40,723 - its best November ever - but its product chief says scant inventories of key models could create customer satisfaction problems.

Mike O’Brien, Hyundai’s vice president of product and corporate planning, told Automotive News that the brand has less than a 20-day supply of the Hyundai Sonata, Tucson and Santa Fe - three of the brand’s best selling-vehicles.

“We need to have at least above 30 (days) to have reasonable availability for our customers to find the vehicle they want,” he said at a Hyundai press event here. “So it’s a satisfaction challenge that we need to address.”

For example, even though the new Sonata has been on sale for a full year and 2010 sales will likely hit 200,000 units by year end, Hyundai still only has a 16-day supply.

Hyundai’s plant in Montgomery, Ala., builds the Sonata and recently began producing the new Elantra compact, which is scheduled to go on sale in January.

The plant has an annual capacity of about 400,000 units and has been running nearly full tilt to keep pace with demand for the Sonata. Sales of the Sonata have jumped 65 percent in the first 11 months to more than 180,000.