Wal-Mart is telling Amazon game on.

The big-box retailer is reportedly warning some tech companies that if they want Wal-Mart's business, they can't run applications on Amazon's cloud platform, Amazon Web Services, some tech companies told The Wall Street Journal.

Wal-Mart uses some tech vendors' cloud apps that run on AWS, Wal-Mart spokesman Dan Toporek told the Journal, though he declined to say which apps or how many. But Toporek did acknowledge instances where Wal-Mart is pushing for AWS alternatives, the Journal reported Wednesday.



A representative from Amazon didn't immediately respond to CNBC's request for comment.

Wal-Mart spokesman Toporek told CNBC in an email: "Our vendors have the choice of using any cloud provider that meets their needs and their customers' needs. It shouldn't be a big surprise that there are cases in which we'd prefer our most sensitive data isn't sitting on a competitor's platform."

Wal-Mart doesn't appear to be alone in this push to leave AWS, either.

Other large retailers are reportedly requesting that service providers move away from AWS, the Journal said, citing technology vendors that work with retailers.

Adding to the many growing conflicts of interest, Amazon has confirmed a number of retailers it competes with use AWS, for example GameStop.

The battle between Wal-Mart and Amazon is only heating up, after Amazon announced plans last week to acquire brick-and-mortar grocery retailer Whole Foods. With Amazon stepping into Wal-Mart's turf in grocery, Wal-Mart has been trying to beef up its e-commerce presence.

Following news last week of an Amazon-Whole Foods buy, Wal-Mart's stock sank more than 7 percent.

An Amazon spokeswoman told the Journal that Wal-Mart's latest moves are attempts to "bully" vendors.

"Tactics like this are bad for business and customers," the spokeswoman told the publication.

Read the complete story from The Wall Street Journal here.