Wal-Mart Stores, Inc. (NYSE:WMT) will kick off the final leg of first quarter earnings season this week, along with retailers Target Corporation (NYSE:TGT), Home Depot Inc. (NYSE:HD), Lowe's Companies, Inc. (NYSE:LOW) and Best Buy Co Inc. (NYSE:BBY). Getty

Wal-Mart Stores Inc. said it launched a free 30-day trial of ShippingPass, its two-day shipping program to all shoppers in the United States, as the world's largest retailer looks to take on Inc.'s Prime subscription service.

Wal-Mart also said existing ShippingPass holders will get a month free, as the company builds on initiatives it announced earlier this month.

Shoppers cart their purchases from a Walmart store in Mexico City, April 24, 2012. Reuters/Edgard Garrido

The company had announced a slew of programs, including online grocery pickup and a partnership with ride-hailing app Uber to deliver groceries as it looks to boost online sales.

The ShippingPass, priced at $49/year, looks to compete with's Prime subscription, which costs $99/year.