Walmart (NYSE: WMT) announced on May 28 that it is expanding its 30-minute-or-less delivery service, now available across 33 cities in the United States.

The announcement came just two weeks after competitor Amazon said it was expanding its own 30-minute delivery services to dozens more cities, with plans to extend further by the end of the year.

Tracy Poulliot, chief eCommerce officer for Walmart U.S., said in a press release: “Customers are looking for faster, easier ways to get what they need in the moments that matter.”

Poulliot added: “We’ve been delivering orders in 30 minutes or less for more than a year, and today 26% of our Express Deliveries are already arriving in that timeframe.”

Walmart said the expanded service builds on its long-term convenience strategy and broader Express Delivery offering, as customer demand grows for more immediate and frictionless shopping experiences.

Customers can shop from more than 100,000 eligible items, including groceries, pantry staples, baby essentials, cold and flu medicine, household supplies, pet food, electronics and prescription delivery.

During the first quarter of the year, Walmart said it completed millions of deliveries in 30 minutes or less, reaching more than 19,000 zip codes across the country.

Walmart noted a trend in “need it now” items across categories, citing examples such as batteries, party supplies, dog food and last-minute meal solutions as drivers of faster delivery demand.

Neil Saunders, a retail analyst at GlobalData, told USA TODAY that fast delivery has become a critical battleground, saying “retailers not offering the service lose out on urgent missions and also run the risk of pushing customers to other platforms for other purchases.”

Saunders added: “Walmart and Amazon are both duking it out on ecommerce, and each is keen not to let the other get the upper hand.”

The 30-minute-or-less service is currently available in Atlanta, Austin, Chicago, Dallas, Denver, Houston, Oklahoma City, St. Louis and several other cities, with further expansion planned.

Customers can identify eligible addresses by looking for the “Delivery in 30 minutes or less” label on the Walmart website or app, and the service is available for a $10 fee for Walmart+ members.

Additional delivery options include express delivery in one hour or less, on-demand delivery in as soon as three hours, and scheduled delivery within a customer-selected window.

During Walmart’s earnings call on May 21, Executive Vice President and Chief Financial Officer John David Rainey said sales utilizing store-fulfilled delivery in the United States had more than doubled over the past two years.

Rainey also noted that more than 36% of orders were delivered in under three hours in the first quarter, and that Walmart could reach approximately 60% of the U.S. population in 30 minutes or less.