TOM KRISHER, AP Auto Writer

DETROIT (AP) — Nearly two years after agreeing to recall 1.56 million older Jeeps that could catch fire in rear-end crashes, Fiat Chrysler U.S. has repaired only 4 percent of the Grand Cherokees and 27 percent of the Libertys covered by the recall.

The figures were detailed in a letter from Chrysler posted Tuesday by U.S. safety regulators.

The rate is below the average of 75 percent 1 ½ years after a recall is announced. It could set up another confrontation between Fiat Chrysler and regulators.

Chrysler makes Jeeps and agreed in June 2013 to install trailer hitches to help protect the gas tanks, which are behind the rear axle and vulnerable in a crash. The company says they’re as safe as comparable vehicles built at the time.