NEW YORK (CNN/Money) Ford Motor Co. announced it was expanding zero-interest financing on some of its 2003 models, following the move made by competitor General Motors Corp. to keep strong sales going into the fall.

On Wednesday Ford announced it would extend its zero-interest offer until the end of September for up to 60-months on most 2002 models, but it declined to extend it to 2003 models, as GM did. Chrysler quietly matched the GM offer for some of its models as well.

Friday it announced it would offer the zero-interest incentive for 36-month financing packages on some but not all of its models, including Ford's Taurus, Windstar, Crown Victoria, Mustang and Excursion, Mercury's Grand Marquis, Marauder, and Sable and the Lincoln Town Car, as well as some of Ford's F-series pickups. But many other top selling-models, including the compact focus and the Explorer sport/utility vehicle, will not have the zero-interest offer available.

"Ford is offering the new incentives to keep its summer sell down going strong and remain competitive on new models," said a statement from Ford. The zero-interest offer on 2003 models runs through the end of September, while the GM offer goes through the end of October. But GM let its zero-interest offer on 2002 models expire.

GM has been a leader on zero-interest incentives since last September, when it introduced the program to keep sales strong in the wake of the terrorist attack. The program produced record U.S. auto sales in October, and strong sales in July and August, when GM reintroduced it to help clear out 2002 inventories.

No. 2 Ford has followed GM by a day or two on its previous zero-interest offers.

Shares of Ford (F: down $0.46 to $10.23, Research, Estimates) were off nearly 5 percent in midday trading Friday following the announcement.