Walmart is stepping up the rivalry against Amazon by taking the fight into the cloud, the Wall Street Journal reported Wednesday.

Walmart warned some tech companies if they want to do business, they can’t run the retailer’s applications on Amazon’s cloud-computing platform, Amazon Web Services, sources told the Journal.

Read: How Walmart Is Speeding Up Its Delivery Processes To Compete With Amazon

Walmart reportedly keeps most of its data on its servers and uses services from emerging Amazon cloud rivals, like Microsoft’s cloud-computing platform Azure. However, Walmart still uses some tech vendors’ cloud apps that run on Amazon’s platform, Walmart spokesman Dan Toporek told the Journal, declining to say which apps or how many. Toporek admitted instances in which Walmart pushed for Amazon alternatives.

“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,” he told the Journal, adding it’s a “small number.”

“Walmart continues to try to bully their suppliers into not using AWS because they have an incorrect view that AWS is somehow supporting Amazon's Retail business,” a spokesperson from Amazon AWS told International Business Times. “Plenty of suppliers are standing up to Walmart and refusing to be told that they can't use the leading‎ infrastructure technology platform (AWS). Tactics like this are bad for business and customers and rarely carry the day.”

IBTimes has also reached out to Walmart for comment.

Read: Amazon Offering Discounted Prime Membership For EBT Card Users

Apart from Walmart, Amazon has other competitors that rely on its cloud platform, such as streaming rival Netflix. Walmart’s moves won’t affect Amazon Web Services' growth, but it could lift rivals.

“People jump through hoops to do business with Walmart all the time,” Gartner analyst Robert Hetu told the Journal. “That should absolutely accelerate the competition from Azure.”

Walmart is also a big influencer. A retailer’s client instructed Snowflake Computing Inc., a data-warehousing service to handle its business from the retailer by running its services using Azure.

“They influence their vendors, which has influence on us,” Snowflake Computing CEO Bob Muglia told the Journal.

Walmart vs. Amazon

Walmart’s moves come after Amazon announced its $13.7 billion deal to buy Whole Foods Market. Amazon’s announcement boosts its rivalry with Walmart, which already sells groceries. Walmart allows customers to order groceries online and pick it up on the same day in select locations.

The retailer has been trying to boost its e-commerce presence as it competes with Amazon.

Walmart tried to rival Amazon Prime memberships by introducing ShippingPass, which resembled Prime’s two-day shipping. Walmart’s membership was priced at $49, half the price of Prime, but the plan failed to launch and was nixed. Although Amazon is more expensive, Prime was a better deal for consumers, since it offered more services, like music streaming and its photo cloud. To come back from its ShippingPass failure, Walmart announced earlier this year its two-day shipping service without a membership.

Meanwhile, Amazon announced this month it’s offering Prime service at a discounted price for people on government assistance programs. The online retailer’s latest move is an effort to reach low-income households, which is a strike at Walmart.