Amazon is expanding its same-day grocery delivery service to 1,000 cities and towns across the U.S., the company said Wednesday.

While the retailer’s same-day delivery expansion leverages its enormous reach online, its fractional brick-and-mortar presence remains a central liability, industry analysts said.

The online retail giant plans to expand the service to 2,300 U.S. locations by year’s end in its quest to compete with Walmart.