SEATTLE, United States — Amazon.com Inc. lowered its free shipping threshold to $25 from $35, undercutting Wal-Mart Stores Inc. by $10 and escalating a battle between the world's e-commerce leader and the world's biggest retailer.

The new threshold shows Amazon competing for shoppers who don’t pay $99-a-year for Amazon Prime, which includes free two-day shipping on millions of items as well as access to music and video. These customers are Amazon’s most loyal shoppers.

The new pricing targets consumers who are more likely to defect to Wal-Mart since the Bentonville, Arkansas-based retail giant offered free two-day shipping on orders of at least $35 while expanding its online marketplace inventory.

Amazon’s non-Prime customers who qualify for free shipping will have to wait longer for their deliveries than Wal-Mart shoppers — five to eight business days, according to the Seattle-based company’s website.

By Spencer Soper; editors: Jillian Ward, Andrew Pollack and Molly Schuetz.