By Deepa Seetharaman SAN FRANCISCO (Reuters) – Amazon.com Inc is preparing for a long battle with Hachette Book Group over a contract dispute that led the U.S. online retailer to curtail sales of some of the publishers books. In a statement on Tuesday, Amazon said Hachette, a unit of French media company Lagardere SCA, has operated in good faith but the two sides remain at odds. The comments, the first by Amazon since the dispute became public in early May, didnt disclose details of the disagreement between the pair. Though we remain hopeful and are working hard to come to a resolution as soon as possible, we are not optimistic that this will be resolved soon, Amazon said in a statement posted online.