Amazon shades Walmart's next-day delivery announcement in snarky tweet

The shipping war between Amazon and Walmart is getting personal.

Jeff Bezos' e-commerce company threw shade at Walmart after the retail giant announced plans for its next-day delivery rollout on Tuesday — just weeks after Amazon said it would invest $800 million to offer free one-day shipping to its Prime members. Amazon didn't immediately provide a timeline for the new option.

In what many consider a jab to Amazon, Walmart said this week it would offer consumers next-day delivery on a "wide range of general merchandise" worth $35 or more without a membership fee. Walmart's NextDay service will kick off in Phoenix, Las Vegas and Southern California, eventually expanding to 75 percent (including "40 of the top 50 major U.S. metro areas") of the U.S. population by the end of the year.

But Amazon wants to remind customers that its one-day delivery option is already available in "thousands of cities."

"Others are trying to up their fast shipping game. Fact is, Amazon customers in thousands of cities across 44 major metropolitan areas already have access to millions of items with free SAME DAY delivery," Amazon tweeted Tuesday afternoon. "Customers are smart – they know the difference."

Bezos took to Twitter hours later to tout Amazon's $1.5 billion new air hub in Kentucky, which he says will get customers their packages even quicker.

"Three million square feet, and it’s going to create 2,000 jobs. And if you’re guessing that driving a front loader was fun, you’re right! #amazon #prime," he posted, along with a video of himself behind the wheel of a tractor at the groundbreaking ceremony.

Amazon has a 50-year lease for about 900 acres at Cincinnati/Northern Kentucky International Airport, where it will handle its own shipping in order to cut costs and get packages to customers quicker.

As of Wednesday afternoon, Walmart hasn't directly responded to Amazon's tweet. In a news release about the upcoming next-day delivery rollout, Walmart focused on the benefits for both itself and customers.

"Our new NextDay delivery isn’t just great for customers, it also makes good business sense. Contrary to what you might think, it will cost us less – not more – to deliver orders the next day. That’s because eligible items come from a single fulfillment center located closest to the customer. This means the order ships in one box, or as few as possible, and it travels a shorter distance via inexpensive ground shipping," the company said.

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Moody’s analyst Charlie O’Shea wrote in a note on Tuesday that Walmart continues to have a “meaningful advantage” over Amazon in the form of 5,300 store locations.

"In addition to providing consumers with same-day availability via in-store pick up of online orders, these stores augment a world-class proprietary distribution network as they are also potential shipping points," O’Shea wrote.

Fox Business' Brittany De Lea contributed to this report.