WASHINGTON — The government has approved $500 million in reimbursements to car dealers for sales under the Cash for Clunkers program and dealers should be paid by late September, officials said today.

Auto dealers have complained that the Obama administration has been slow to pay them for the car purchase incentives of up to $4,500. The rebates led to 690,114 new sales at a taxpayer cost of $2.88 billion.

A U.S. Department of Transportation official said 120,000 submissions from dealers, or about 17 percent, have been approved under the program, which ended on Aug. 24. The official, who spoke on condition of anonymity, was not authorized to speak publicly about the data before a congressional briefing.

All eligible and completed dealer submissions should be fully paid by Sept. 30, the official said.

The official said the department expects to be approving $100 million per day by the end of next week.

The program, which provided incentives of $3,500 or $4,500 for consumers to trade in a gas-guzzler for a new, more fuel-efficient car or truck, boosted car sales during the summer.

Auto dealers have said the delays have squeezed their businesses, leaving them on a short-term hook for dozens of deals. AutoNation, the nation's largest dealership chain, said Wednesday it was owed more than $54 million from clunker sales and expected to get paid in 30 to 60 days.