Many will be shut down for the whole month of January.
Spokesman Tony Sapienza said normal production would be around 750,000 cars and trucks for the quarter.
GM and nearly all automakers who sell in the U.S. are mired in the worst sales slump in 26 years.
Cash-strapped GM is seeking government loans to stay in operation beyond the end of the year. The White House says it may tap the $700 billion Wall Street bailout fund to help GM and Chrysler stay in business after the Senate blocked a measure to provide $14 billion in immediate loans.
