UPDATE 1-GM to lay off 1,500 hourly workers as demand slows

(Adds details on layoffs, background)

DETROIT, Oct 16 (Reuters) - General Motors Corp GM.N will lay off 1,500 hourly workers at plants in Michigan and Delaware where it builds pickup trucks, large cars and a two-seat roadster due to slowing demand, a spokesman said on Thursday.

GM, which posted a $15.5 billion net loss in the second quarter, has been battling an industry sales slump in the United States and signs that sales are slowing globally. Its 2008 U.S. sales were down nearly 18 percent through September.

"The market continues to struggle across the industry," GM spokesman Tony Sapienza said. "We continue to adjust to the demand ... as the economy picks up you will probably see us adjust production upward as well."

The layoffs include 700 workers at a Pontiac, Michigan, assembly plant, as well as 400 each at plants in Hamtramck, Michigan, and Wilmington, Delaware, he said.

GM plans to slow the assembly line at the Pontiac pickup plant where it builds the Chevrolet Silverado and GMC Sierra, effective in February, resulting in 700 layoffs, he said.

The automaker also will slow the assembly line in Hamtramck in January where it builds the Cadillac DTS and the Buick Lucerne, causing 400 layoffs, Sapienza said.

GM plans to cut to one shift from two shifts in Wilmington effective Dec. 8, where workers build the Saturn Sky, Pontiac Solstice and the Opel GT roadsters, he said. (Reporting by David Bailey; Editing by Phil Berlowitz)