Chrysler is refusing a request by the US government to recall 2.7 million Jeeps.
The National Highway Traffic Safety Administration (NHTSA) says they are at risk of fuel tank fires if they are hit from behind in a collision.
The NHTSA asked Chrysler to voluntarily recall Jeep Grand Cherokees from 1993-2004 and Jeep Libertys from 2002-2007.
But the company said in a statement that the Jeeps are safe and it "does not intend to recall the vehicles".
The agency can order a recall, but would need a court order to carry it out.
Refusals on the part of carmakers are rare. Chrysler has until 18 June to respond to the request.
The NHTSA opened an investigation into the models in 2010.
It says that when hit from the rear, the Jeeps' fuel tanks can leak fuel and cause fires.
The location of the tanks behind the axle and their height above the road is a design defect, the NHTSA told Chrysler in the letter requesting the recall.
Chrysler moved the Grand Cherokee's fuel tanks ahead of the rear axle in 2005, and did the same thing with the Liberty in 2007.
However, recalling and refitting the older Jeeps would be time-consuming and costly.
In 2011, when Toyota recalled 1.7 million cars for possible fuel leaks from sensors, an analyst estimated the cost at $240m (£157m).
The NHTSA said it had evidence of at least 32 rear-impact crashes and fires in Grand Cherokees, causing 44 deaths.
It also found at least five such crashes in Libertys, causing seven deaths.
As part of its investigation, the NHTSA claims the older Grand Cherokees and Libertys have fatal crash rates that are about double those of similar vehicles.
http://www.bbc.co.uk/news/business-22777489
