SAN BRUNO . (AP) — Wal-Mart Stores Inc., the world's largest retailer, said Tuesday that it's going to set up lockers in about a dozen stores so that shoppers who order on its website can pick up their items without having to wait in a checkout line.

The test, which is being conducted during the summer in an undisclosed market, is part of Wal-Mart's strategy to offer more convenience for web-savvy shoppers to make their purchases wherever they want.

Wal-Mart officials disclosed the test at a media event at the company's global e-commerce offices in San Bruno, Calif., located in Silicon Valley. Wal-Mart, which is based in Bentonville, Ark., is using the one-day event to showcase how it's meeting the growing challenge of fending off competition from online rivals eBay Inc. and Amazon.com.

The discounter also is following its own customers. More than half of Wal-Mart shoppers have smartphones. And one third of Wal-Mart's online traffic comes from mobile phones.

Over the past year, Wal-Mart has been launching a number of initiatives that merge its online business with its 4,000 physical stores. That includes same-day delivery in five markets and an app that allows shoppers to scan their purchases while in the aisles before paying at self-checkout lanes.

With the new lockers, online shoppers will get a password they can use when they pick up the items at in-store lockers. Company officials declined to say what the lockers look like.

The service builds on another option called "site to store" that was launched in 2007. That service allows shoppers to order online and then pick up the items at a special counter within two weeks.

"We're tenacious about building best in class e-commerce," said Neil Ashe, president and CEO of Wal-Mart's global e-commerce division.