Amazon has reportedly halted pre-orders of some Disney films, in what looks like another contract dispute following the online retailer's row with a book publisher.
Physical copies of titles such as Maleficent and Captain America: The Winter Soldier were unavailable for order on Amazon.com.
Digital copies of some of the movies in question were still available for pre-order, the Wall Street Journal reported.
Amazon has been waging a battle against Hachette Book Group, the fourth-largest US book publisher, over the price the online retailer can charge for e-books.
A group called Authors United ran a two-page ad in the New York Times on Sunday, criticising Amazon for halting pre-orders from some Hachette authors and slowing delivery of books by Hachette authors.
The ad was signed by more than 900 writers, including Stephen King and Donna Tartt.
Amazon.com's Books Team ran a message on the Readers United website reiterating its arguments for cheaper ebooks, and suggested people email Hachette chief executive Michael Pietsch.
Scarlett Johansson stars in the latest Captain America film
"Once again, we call on Amazon to withdraw the sanctions against Hachette's authors that they have unilaterally imposed, and restore their books to normal levels of availability."
Amazon argues that cheaper e-books sell more copies and so ultimately generate more revenue and more royalties for authors.
