The retailer, which gets 56% of its annual U.S. sales from its food business, said on Monday it was bringing the online grocery delivery service it is testing with Uber to two more cities, Orlando and Dallas, taking to six the number of markets it is testing this important service in ahead of a likely roll-out to many more markets down the road. The delivery option is currently available in Denver, San José, Phoenix and Tampa.

The expansion is just the latest step Walmart is taking to counter Amazon’s big grocery push, one that will get more intense once its acquisition of Whole Foods Market (WFM) closes this year. Walmart has so far focused more on using many of its thousands of stores as a customer drive-in pick-up for online grocery orders, a feature now available at 900 of its locations, than delivery. Yet there is no denying that delivery proper has to become part of Walmart’s offering: just last week, German deep discounter Aldi announced it was launching grocery home delivery in a few markets.

Last week, Wal-Mart Stores, Walmart’s parent company, announced a 12th straight quarter of rising comparable sales in the United States, much of that attributable to what it said was the $160-billion-a-year grocery business’ best quarter in five years.

After a customer has placed an online order with Walmart and chosen the delivery option, Walmart workers will pick items, scan them as they work through the store, and then call an Uber driver to come retrieve the order and deliver it to the customer’s destination, all with a few to providing the convenience shoppers increasingly demand.

“We’re working hard to find a way to get you fresh, quality groceries all while keeping a little more time on your calendar,” Mike Turner, vice president of e-commerce operations, wrote in a Walmart blog post.