It appears that Amazon is getting antsier with its business partners which do not want to pay it huge amounts of cash.

For the past month Amazon has been in a public dispute with Hachette, a major publisher, over terms for e-book sales. Some Hachette books have suffered from shipping delays while others have been stripped of their customary discounts.

Now it seems that Amazon has turned off the preorder function for DVDs of prominent Warner Bros. films as it seeks to raise pressure on the company during negotiations. "The Lego Movie," for example, is listed as "currently unavailable" on Amazon. Set for release in the home video marketplace on June 17, there is no option to place a preorder. A spokesman for Warner Bros. declined to comment, citing a policy "to not comment on contract points or any proprietary issues involving our partner.

Amazon has said that it is all part of the normal negotiation process, however it might want to be a little careful that it does not hack of anti-trust regulators.