Walmart store employees are now delivering packages to customers' homes. Getty Images Walmart is now using store employees to deliver packages to customers' homes in the retailer's latest effort to undercut Amazon.

Here's how it works: store employees who opt into the program are given packages at the end of their work shifts, with a list of delivery addresses.

The addresses are all on the employees' routes home from work — meaning they don't need to go far out off their routes home to deliver the packages.

In a blog post Thursday, Walmart e-commerce head Marc Lore called the program a "game-changer," saying it has resulted in next-day deliveries for many customer orders.

He said it's a win for both employees and customers, since employees get paid for the deliveries and customers are getting their online orders delivered sooner.

The program is still in test phase and only available at three stores so far — two in New Jersey and one in northwest Arkansas.

It will likely roll out to more stores soon, since according to Walmart, the response from associates and customers has been overwhelmingly positive.

"Walmart has strength in numbers with 4,700 stores across the U.S. and more than a million associates," Lore wrote in his blog post. "Our stores put us within 10 miles of 90% of the US population. Now imagine all the routes our associates drive to and from work and the houses they pass along the way."

Workers stock shelves in a newly built Walmart store. Thomson Reuters Lore also highlighted that this new program is different from crowdsourced delivery because of its efficiency in determining delivery routes for employees that follow their routes home from work.

"Unlike crowdsourced delivery, where the driver has to travel (often out of the way) to pick up the package, then drive the full distance to deliver it, our associates are starting at the same place as the packages," he wrote. "Once they're done working at the store for the day, they pick up the packages from the backroom, load them into their vehicle, enter the delivery addresses into the GPS on their phone and head towards home."

The program is the latest in a string of new services and discounts that Walmart has rolled out this year in an effort to fend off competition from Amazon.

In February, the retailer launched free two-day shipping for all orders over $35 — a direct challenge to Amazon's $99 Prime membership, which offers free two-day shipping on all orders.

Walmart also recently rolled out a new discount to customers who ship purchases to one of Walmart's more than 4,700 US stores instead of to a home or elsewhere. The discount gives customers as much as $50 off purchases of large items like televisions.

Walmart's investments appear to be working.

The company's e-commerce sales soared by 63% in its most recent quarter, compared with 29% growth the prior quarter. The company said most of these sales were organic through Walmart.com. Walmart's $3 billion acquisition of the online retailer Jet.com, which Lore founded, also helped the company boost e-commerce sales.