HIGHLAND PARK, Mich. (AP) _ Chrysler Corp. Chairman Lee Iacocca apologized Wednesday to buyers of cars that were test-driven with disconnected odometers, promising to extend warranties on thousands of cars and replace those that were damaged in testing.

Chrysler was indicted last week along with two of its executives on federal charges of test-driving 60,000 cars with the odometers disconnected and of selling some badly damaged cars as new.

''Our big concern is for our customers, the people who had enough faith in Chrysler to buy a vehicle from us,'' Iacocca said. ''We did do something to have them question their faith in us.

''Did we screw up? You bet we did,'' he added.

Iacocca said, however, that the No. 3 automaker does not believe it did anything illegal.

The indictment covers 18 months beginning in July 1985. Chrysler says it has left the odometers connected on cars during testing since October 1986.

Iacocca said of 72 cars that company or insurance records indicate were damaged in testing, 32 were scrapped or sold at auction and 40 were sold as new. Customers who bought the cars as new will receive a comparable new Chrysler replacement vehicle, he said.

Owners of cars driven with disconnected odometers during the period covered by the records, when Chrysler's warranty was five years or 50,000 miles, will get warranty extensions to seven years or 70,000 miles.

The extended warranties will cover brakes, electrical parts, air- conditioning , suspension and steering in addition to the regular powertrain coverage, Iacocca said.

Owners, who will be notified through the mail beginning Thursday, also will be given a free inspection of their cars and free repair of any problems found in the inspection, he said.

Full-page advertisements describing the program will be published in newspapers across the country Thursday and in magazines early next week, he said.

Iacocca, who joined Chrysler in late 1979, said he was unaware the company still tested cars with disconnected odometers until the federal investigation began.

General Motors Corp. and Ford Motor Co. have said they began leaving odometers connected in their overnight test programs beginning in 1973.

Iacocca would not estimate the cost of the replacement and warranty extension, but added ''money's no object'' and said Chrysler wanted only to repair its image.

He said neither the replacements nor warranty extensions meant the company was admitting guilt in the federal case or in the three class-actions suits that Chrysler attorneys said have been filed so far.