Amid a tense negotiation over contract terms, Amazon has delisted e-book titles distributed by German digital distribution and publishing services company Bookwire.

While the exact number of delisted titles is not known, Bookwire distributes more than a million titles for some 2,300 publishing companies around the world. Bookwire operates primarily in Germany, but also in the English, French, Portuguese and Spanish-language markets, among others. The delisting impacts all Bookwire titles worldwide and has been ongoing for more than a week.

Bookwire's existing contract with Amazon ran out earlier this year and the two companies have been unable to reach a new agreement.

Citing declining margins and increased costs, Bookwire explained in a letter to customers that it could not accept "Amazon's current offer." Bookwire went on to assure customers it was working to find a solution to the impasse. "This cannot be in the interests of Amazon customers in the long term," the letter states. "Since Amazon sees itself as 'customer-centric' and we are still in constructive discussions, we are working with Amazon to find a quick solution to secure the long-term partnership on reasonable terms."

Amazon has since released a statement to the press, saying, "During months of contract negotiations, Bookwire insisted that Amazon’s only path to continue giving Kindle readers access to titles of publishers Bookwire exclusively distributes was to accept a significant move backwards in economics from the terms under which our two companies have successfully operated for years. Our contract with Bookwire has ended, and we regret that we had no choice but to remove the ebook content they distribute to comply with the expiration of our contractual right to sell it."