DETROIT — In one of the biggest-ever showdowns between an automaker and the government, Chrysler on Tuesday is expected to file papers explaining its refusal to recall 2.7 million older Jeep SUVs that are at risk of catching fire in rear-end collisions.

The government says 51 people have suffered fiery deaths in Jeep Grand Cherokees and Libertys with gas tanks mounted behind the rear axles. But Chrysler is expected to stick to its contention that the SUVs are as safe as similar vehicles on the road. The Jeeps, it says, met all federal safety standards when they were built, some more than two decades ago.

Car companies rarely spar publicly with the National Highway Traffic Safety Administration, the agency that monitors auto safety. The last time an automaker denied a NHTSA recall request was early in 2011, when Ford said calling back 1.2 million pickup trucks for defective air bags wasn’t justified. Ford later agreed to the recall after NHTSA threatened to hold a rare public hearing on the issue.

NTSHA could employ the same tactic in the Jeep case. The Jeep dispute ultimately could be decided in federal court.

NHTSA began investigating the SUVs three years ago at the behest of Clarence Ditlow, director of the Center for Auto Safety, an advocacy group.

Earlier this month, NHTSA sent a letter to Chrysler asking it to voluntarily recall Grand Cherokees from 1993 through 2004 and Libertys from 2002 through 2007.