AutoNation Inc. said its March retail new vehicle sales increased 19 percent compared to a year ago, but the nation's largest dealership group warned today the Japanese earthquake will "significantly impact" product availability in the second and third quarters.

Japanese manufacturers have been forced to idle plants and curtail output because of parts shortages, rolling blackouts and damage following the quake and tsunami, reported Automotive News.

"We expect production disruptions will significantly impact product availability from Japanese auto manufacturers in the second and third quarters of 2011," AutoNation CEO Mike Jackson said in a statement today. "The situation is still developing, and at this time it is difficult to fully predict the impact of the production disruption on the industry and our business."

Japanese manufacturers accounted for 52 percent of AutoNation's total new unit sales in 2010, and approximately two-thirds of those units were assembled in North America, the company said.

The retailer, which owns and manages 243 new vehicle franchises in 15 states, will provide additional information when it releases first quarter financial results on April 26.

Despite concerns about gas prices and the quake, AutoNation said the auto retail market and underlying consumer demand will continue to recover throughout 2011.

"Our planning assumption for 2011 industry new unit sales remains 12.8 million units, and we believe that we will manage through these production shortfalls," Jackson said.

In March, AutoNation's retail new vehicle unit sales totaled 22,246, up 23 percent from a year ago. Overall, automakers reported that U.S. light vehicle demand rose 17 percent last month to 1.2 million units.

AutoNation said March new retail sales of General Motors, Ford and Chrysler models rose 21 percent to 6,320 units. Import sales rose 19 percent to 12,194 units and demand for premium luxury models rose 13 percent to 3,732 units.

During the first quarter, retail new vehicle sales increased 23 percent to 54,198 compared to the first quarter of 2010.