NEW YORK — Subway is shaking up its loyalty rewards program, giving customers the ability to earn $2 discounts instead of free Footlongs.

The changes, taking place next month, are part of Subway’s attempts to revamp its image, lure people back to its restaurants and fight falling sales. Sales at Subway’s U.S. stores fell more than 4 percent in 2017 from the year before, according to food industry tracker Technomic, as it faced increasing competition from other sandwich chains and those selling burgers and fries. Loyalty programs are seen as a way to keep customers returning and spending more.

Subway said customers will have the ability to earn points at more restaurants: Only a third of its locations in the U.S. and Canada, or 9,500 restaurants, participated in the program being phased out. About 28,500 of its U.S. and Canadian locations will participate in the new one, the company said.

Customers who spend $50 will get a $2 discount they can use on sandwiches, salads or any other menu item. The previous program gave those that spent $50 a free 6-inch sandwich; those that spent $75 earned a free Footlong. Subway said customers can save up enough $2 discounts to get a Footlong, which costs about $5. The $2 discount, however, expires within 90 days.

There will be free cookies and chips for those who visit more often, said Carissa Ganelli, chief digital officer.