Walmart made headlines last week when the Wall Street Journal reported that a third-party vendor, New York-based Jewelry Unlimited, was selling a $18,000 diamond watch by Cartier on walmart.com on Black Friday.

But Cartier took aim at Walmart on Monday and said it could not vouch for the authenticity of the watches sold via walmart.com. (Walmart does not take possession of items sold in its marketplaces. It simply provides the e-commerce infrastructure and charges a fee to the vendor.)

“Wal-Mart is not a Cartier authorized retailer therefore Cartier has no knowledge or involvement in the selling or marketing of this watch nor can confirm the authenticity of the piece,” Cartier, a unit of Swiss luxury conglomerate Richemont, said in a statement. But the statement did not explicitly call on Walmart to stop selling the watches.

Cartier did not respond to a request by Fortune for comment. Jewelry Unlimited web site lists Cartier as a brand it sells, but Jewelry Unlimited could not be reached to comment about whether it is an authorized Cartier dealer.

As for Walmart, it said in a statement to Fortune, “If we get complaints about the authenticity or source of a product, we will work with the customer and the seller, and may remove the product from our site.”

For a company like Cartier, being sold at Walmart can be seen as potentially damaging to its luxury aura. Cartier tries to control the distribution of its goods by selling its products solely through its own stores and authorized retailers. Cartier acknowledges that its products can be found in unauthorized stores, both online and brick-and-mortar, raising the risk that faulty or even fake Cartier items may be sold to unwitting customers.

Cartier watches were also available on Amazon as of Monday evening. In the past, Cartier has been aggressive about protecting its brand identity by suing the likes of Amazon, HauteLook, and Apple (AAPL)over in various intellectual property cases. Amazon.com currently lists several Cartier items.

Earlier this year, Walmart completed a massive upgrade of its marketplaces as it looks to compete with eBay (EBAY) and Amazon.com (AMZN) more effectively. There are now 23 million different products on the site, up from 8 million a year ago, allowing Walmart to offer more upscale brands like Michael Kors (KORS) online than it has in stores.

Last year, Tiffany & Co (TIF) successfully sued Costco Wholesale over the sale of engagement rings that the bulk retailer called “Tiffany” by using an argument similar to Cartier’s.