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.

Amazon will begin same-day fresh grocery deliveries in more than 1,000 U.S. cities. It’s free for orders over $25 for Prime members.

Subscribers to Amazon.com's Prime service can now get strawberries, milk, meats and frozen dinners on the same day they order them as the company expands its fast-delivery option to perishable food items,