DETROIT  General Motors expects to lay off thousands of factory workers after the number who voluntarily quit through a recent buyout and early retirement program fell short of the carmaker’s target.

G.M. said Monday that about 6,000 hourly workers had left as of Saturday. That means the company still has about 48,000 hourly workers, which is 7,500 more than its year-end goal of 40,500.

A G.M. spokeswoman, Sherrie Childers Arb, said the company planned to meet with the United Automobile Workers union to determine how it could meet its goal by Dec. 31, but she said the company was not considering another buyout offer.

“Some people will go into a layoff situation,” Ms. Childers Arb said. “Others will be offered positions at other G.M. facilities. But we probably would not be able to find positions for all of those workers.”