General Motors' 6,000 workers at the company's two Lansing, Michigan assembly plants will get only one week off this July, rather than the customary two, Associated Press (AP) reported.

Citing spokeswoman Kim Carpenter, AP said that GM has scheduled full production of 10,000 cars for the second week in July.

Workers at the two plants are already working overtime to build the Pontiac Grand Am, Oldsmobile Alero and Chevrolet Malibu, AP said.

Carpenter told the news agency that demand is picking up, although the models have sold poorly in recent months.

The change is causing problems for employees who have already scheduled holidays, AP said.