Amazon boxes are seen stacked for delivery in the Manhattan borough of New York City, January 29, 2016. REUTERS/Mike Segar/File Photo

(Reuters) - Amazon.com Inc AMZN.O said on Tuesday it cut the threshold for free shipping to $25 from $35, upping the ante against Wal-Mart Stores Inc WMT.N in a hotly contested battle for ecommerce supremacy.

Amazon already offers free two-day shipping under its $99 Prime membership program but the new offer is aimed at encouraging more customers to shop on its platform.

Amazon also hopes to convert these shoppers to Prime members down the line.

The world’s biggest retailer, Wal-Mart, has been building up its ecommerce business through acquisitions such as Jet.com, as it looks to narrow the massive gap with Amazon.

Wal-Mart started its own membership program called ShippingPass last year, which offered free two-day shipping for $49 a year. However, the company ended the program in January, replacing it with free two-day shipping on orders of $35 or more.