WASHINGTON — A negotiation aimed at regulating repair of rental vehicles with defects has bogged down, dimming hopes of passing legislation that has become the focus of a nationwide Internet campaign.

Clayton, Mo.-based Enterprise Holdings, a key player in the talks, is being accused by consumer advocates of seeking loopholes that would let companies rent and sell cars under recall for safety reasons without getting them fixed.

Enterprise says it has joined with all major rental firms — except Hertz — in supporting legislation that would, for the first time, give the government authority over rental company policies for recalled autos.

Hertz has embraced a compromise with consumer advocates that is stricter than corporate rivals like Enterprise will accept.

Until earlier this year, privately-held Enterprise, which owns the National and Alamo rental companies, had insisted that any legislation was unnecessary.

But in February, Enterprise relented after becoming the target of an Internet protest pressing the company to support a regulatory bill in Congress. As of this week, more than 160,000 people had signed the Enterprise Rent-a-Car petition at Change.org.

The online protest was organized by Carol Houck, the mother of two California sisters who died in a fiery crash eight years ago while driving a vehicle rented from Enterprise. A jury awarded the Houck family $15 million two years ago after testimony that the vehicle, a PT Cruiser, had a power steering fluid leak that had gone unrepaired.