Amazon.com and Barnes & Noble, aiming to head off competition from Apple, will give publishers control over pricing for electronic versions of books, according to three publishing executives.

Amazon.com will let publishers set prices, abandoning its practice of charging $9.99 for many new releases and bestsellers, said the executives, who asked not to be identified because negotiations aren’t public. Barnes & Noble’s policy change will take effect by Friday, when Apple starts shipping its iPad tablet-style computer, two of the executives said.

Sony, the maker of three digital book readers, said Wednesday that several major publishers will set the price of most e-books at $12.99 to $14.99, a shift from retailers deciding the pricing. All three booksellers, which together dominate the electronic-book market, are changing tack to keep from losing customers to the iPad, which lets users read books, browse the Web and view videos.

“It’s not at all a coincidence this is the same weekend the iPad becomes available,” said James McQuivey, an analyst at Forrester Research Inc. in Cambridge, Mass. “It was really the iPad that served as the catalyst.”