Walmart will soon cut gasoline prices by up to 15 cents per gallon for drivers in 20 U.S. states who pay with its cards in a bid to appeal to loyal shoppers hit by big price increases at the pump.

Patrons paying with a Walmart MoneyCard or Walmart credit card will save 15 cents per gallon from Aug. 31 through Dec. 24, while others who use a Walmart gift card will get 10 cents off, Wal-Mart Stores Inc said on Wednesday.

The promotion comes as Wal-Mart, the world's largest retailer, tries to attract shoppers heading into the holiday season. Last week, Walmart said it would bring back layaway a month early, giving U.S. shoppers under economic pressure more time to pay for holiday gifts.

"Our customer remains pressured from the economy," said Walmart U.S. Chief Merchandising and Marketing Officer Duncan Mac Naughton, echoing comments Wal-Mart made earlier this month that shoppers' top concerns are jobs, gas prices and higher food costs.

The latest "gas rollback," at more than 1,000 gas stations, follows a similar 2011 program that ran for a longer period of time and offered savings of 10 cents per gallon. Last year's promotion ran from June 29 through Christmas Eve.

When gas prices rise dramatically, shoppers often make fewer trips to stores and buy more on each visit.

Gasoline prices are not at record highs but have been rising in recent months and jumped this week as Hurricane Isaac threatened to batter the U.S. oil refining belt. Any significant damage to refineries or extended outages could push gas prices higher.

After Hurricane Katrina, a Category 3 storm, battered the Gulf coast in 2005, U.S. gas prices jumped more than 45 cents in a single week.

The average price for regular gasoline was $3.80 on Wednesday morning, up from nearly $3.49 a month ago and $3.61 a year earlier, according to AAA data. In July 2008, the average price hit an all-time high of $4.11.

Throughout the year, Walmart offers smaller gas discounts to card holders at stations near its stores in 22 states run by Walmart or Murphy USA. In most of those states, Walmart credit card holders get 5 cents off per gallon year-round, while those paying with a Walmart MoneyCard or gift card get 3 cents off.

Walmart is not alone in trying to woo shoppers with lower-priced gasoline.

Grocery chain Kroger Co often offers gasoline discounts to loyal patrons. D uring a summer promotion this year it is doubling the number of points card holders can earn, allowing for discounts of up to $2 off per gallon.

Warehouse clubs Costco Wholesale Corp, Wal-Mart's Sam's Club and BJ's Wholesale Club monitor prices at nearby stations and try to match or undercut them to lure drivers.