Aug. 21 (Bloomberg) -- Nissan Motor Co., the third-largest Japanese carmaker, led auto shares lower in Tokyo after the U.S. said a “cash for clunkers” vehicle trade-in program will end next week and the yen gained against the dollar.

Nissan slid as much as 4.6 percent to 681 yen at the 11 a.m. trading break. Honda Motor Co., Japan’s second-largest carmaker, dropped 3.9 percent and Toyota Motor Corp., the biggest, fell as much as 3.2 percent to 3,970 yen and traded at 3,990 yen.

The clunkers program will end on Aug. 24 after helping boost auto sales in the U.S., where the three Japanese carmakers traditionally earn at least half of their operating profits. Governments worldwide are providing stimulus money aimed at spurring auto demand amid the industry’s worst market in three decades.

“There may have been hope that the program would be extended,” said Yoshiaki Kawano, an auto-sales analyst at CSM Worldwide in Tokyo. “There’s also concern that the sales gains from the program just pushed forward trade-ins that would have happened next year.”

The program, which offers auto buyers discounts of as much as $4,500 to trade in older cars and trucks for new, more fuel- efficient vehicles, has recorded more than 457,000 dealer transactions worth $1.9 billion in rebates, the U.S. Department of Transportation said yesterday.

The yen also gained against the dollar, cutting the value of repatriated earnings from overseas sales. The dollar was at 93.92 yen from 94.19 yen yesterday.

Toyota based its full-year forecast on an exchange rate of 92 yen to the dollar. Honda’s was based on a rate of 91 yen to the dollar.

To contact the reporter on this story: Makiko Kitamura in Tokyo at mkitamura1@bloomberg.net.

Last Updated: August 20, 2009 23:16 EDT