The two companies agreed to the boost in volume in a recently signed amendment to a 13-year contract announced in 1999, IMCO said in a statement. The plant is expected to start ramping up capacity by the end of 2004.

IMCO spokesman Paul Dufour told Reuters that the plant's capacity in total will be around 280 million pounds of aluminum alloy products, solely produced for GM, the world's largest automaker.

IMCO chairman and CEO Don V. Ingram said in the statement, "With this new supply requirement, IMCO will add additional melting, processing and environmental equipment at our Saginaw plant in order to provide the increased alloys shipments."

GM and other auto makers are increasing their use of aluminum to minimize vehicles' weight while maintaining their size, IMCO said, "thus satisfying customer preferences while reducing fuel usage and greenhouse gas emissions."

Aluminum-intensive vehicles provide better acceleration, braking, and handling, IMCO said.

The company noted that in North America over the past 12 years, the use of aluminum has doubled in cars and tripled in SUVs, light trucks and minivans.