After testing the grocery delivery membership program in Houston, Miami, Salt Lake City and Tampa earlier this year, it’s now expanding the program to 1,400 additional stores this fall. It plans to make the service available to half of the country by the end of the year.

Delivery Unlimited, while it’s, well, limited to groceries, has been frequently compared to Amazon’s Prime program. Members pay $98 per year (or $12.95 per month) to receive as many Walmart grocery deliveries as they want. The program comes with a 15-day free trial. Walmart also offers grocery pickup at 3,100 stores.

“We’ve been investing in our online grocery business by quickly expanding our grocery pickup and delivery services,” said Tom Ward, senior vice president of digital operations at Walmart U.S., in a statement “Delivery Unlimited is the next step in that journey.”

Amazon is a serious competitor, though, with U.S. e-commerce sales that are eight times the size of Walmart’s. And Prime members can have much more than groceries delivered, which could be a challenge for Walmart.

The company has already taken steps to quiet that criticism. Earlier this year, Walmart announced it would offer free one-day delivery on many items for orders over $35 to battle Amazon’s free shipping for Prime members.

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