Jan. 14 (Bloomberg) -- Nissan Motor Co., Japan’s third- largest automaker, said its U.S. auto-assembly plants will build vehicles only four days a week instead of five to adjust to slumping demand.

The schedule change will continue “indefinitely,” a spokesman, Steve Parrett, said today. Nissan builds models including the Altima sedan and Frontier pickup in Smyrna, Tennessee, and the Titan pickup in Canton, Mississippi.

“We don’t know when it might change or if it might change,” said Parrett, who didn’t give specifics on U.S. volume.

The move deepens the U.S. production cuts put in place in 2008 by Nissan, which posted an 11 percent drop in sales in the world’s biggest auto market. Tokyo-based Nissan offered early- retirement incentives to U.S. workers last year as it joined Toyota Motor Corp. and Honda Motor Co. in paring output.

Nissan’s U.S. operations are based in Franklin, Tennessee. The company’s American depositary receipts fell 6 cents to $6.91 at 12:32 p.m. in Nasdaq Stock Market composite trading.

An engine plant in Decherd, Tennessee, also will reduce production, using a different approach, Parrett said. He said he didn’t know whether Nissan’s two Mexico auto factories would be affected.

To contact the reporter on this story: Alan Ohnsman in Los Angeles at aohnsman@bloomberg.net

Last Updated: January 14, 2009 12:38 EST