Inc. isn't accepting pre-orders for Warner Bros. movies on its website, the latest of the online retailer's contract feuds to spill into public view.

Customers trying to pre-order films such as "The Lego Movie," "300: Rise of an Empire" and "Winter's Tale" are instead asked to sign up to be notified when the item becomes available. Digital downloads are available through Amazon Instant Video.

The world's biggest online retailer is seeking concessions from Warner Bros. that would give it more of a margin on sales of DVDs and digital versions of its movies, said a person familiar with the matter, who asked not to be identified because the negotiations are private.

Amazon is already in a standoff with Hachette Book Group over e-book pricing in a tussle that will help determine whether publishers can gain leverage against the online retailer and biggest seller of e-books. To ratchet up pressure on Hachette, Amazon started delaying shipments and blocking some book pre-orders.

Contract disputes between a retailer and suppliers aren't new, yet keeping certain items from consumers is rarer. Amazon's strategy contradicts its longtime philosophy of giving customers a simple way to order almost everything online.

The discussions with Time Warner and Hachette follow investor pressure on Amazon to become more profitable. The company makes less than 1 cent in profit for every dollar in revenue it generates, as Chief Executive Jeff Bezos spends on fulfillment centers, grocery delivery and new products like the smartphone it's expected to unveil at an event in Seattle next week.

Keith Cocozza, a spokesman for New York-based Time Warner, the owner of Warner Bros., declined to comment. Representatives for Seattle-based Amazon didn't immediately respond.

Bloomberg News