TOKYO - Mitsubishi Motors Corp. said Tuesday it will halt production at its biggest plant in Japan for three weeks in February to cope with mounting inventories of unsold vehicles amid a deepening global downturn.

Japan's fourth-largest automaker said the move will affect its Mizushima plant in western Japan, which has annual production capacity of 600,000 units. The Mizushima plant mainly produces passenger cars.

"We have to reduce our inventories. The root cause of this problem is a prolonged slump in the global auto market," said a Mitsubishi Motors spokesman.

The Mitsubishi Motors North America plant in Normal also will stop production, for seven weeks, starting in mid-February. Non-production will begin Feb. 16, and workers will begin to build cars again April 6.

MMNA sold 97,257 vehicles in 2008, a nearly 25 percent decrease from the 128,993 sold the previous year. It was the company's worst performance in at least the past decade.

Apart from the Mizushima plant, Mitsubishi Motors runs two other auto factories in Japan - one in Aichi, central Japan, and another in neighboring Gifu. The spokesman said the Aichi plant will be running for only 16 days in February and the Gifu plant will open for just nine days.

The Aichi plant makes compact cars and SUVs and has annual production capacity of 180,000 units. The Gifu factory also produces SUVs, such as the popular Pajero, and has capacity of 130,000 units.

Faced with slumping sales at home and abroad, Mitsubishi Motors has forecast its net profit will likely drop by 42 percent to 20 billion yen ($220 million) in the current financial year ending March 2009.

Japanese automakers have been cutting jobs and production to cope with shrinking global demand. Japan's No. 1 automaker, Toyota Motor Corp., is forecasting a 150 billion yen operating loss for the current fiscal year - its first such red ink in 70 years.