General Motors will eliminate about half the work force at its Martinsburg, West Virginia, plant over the next few years, the company said on Wednesday.

Katie McBride, a spokeswoman for GM Service and Parts Operations, told the Associated Press (AP) between 50 and 100 jobs will be moved out of the plant within the next six months as the company shifts packaging responsibilities to three processing plants in Michigan. The remaining 150 to 200 processing jobs will be moved within the next several years, she said.

GM's Martinsburg complex employs about 440 workers, according to AP. The remaining distribution centre provides parts to GM dealers in Delaware, Maryland, New Jersey, Pennsylvania, Virginia and West Virginia.

"We are - like everyone else in the automotive industry - under tremendous pressure to improve customer satisfaction and improve operational efficiency," McBride told the news agency. "We've analysed our supply chain strategy, and looked at how we can better serve the customer and streamline our delivery process."

Under a contract with the United Auto Workers, the transferred positions are not considered layoffs. Workers will be given the option to move to other GM plants or other work will be found for them in the Martinsburg area, McBride reportedly said.

The Associated Press noted that GM previously trimmed more than 200 jobs from the Martinsburg plant's work force when it opened a $US26 million, 380,000-square-foot parts distribution centre in 2001. That investment had allayed earlier fears that GM might leave the state entirely.