Producers are worried that the release of the next Harry Potter novel will affect trade, particularly interest in Tim Burton's Charlie and the Chocolate Factory.

Burton's adaptation of the Roald Dahl book is released this weekend in the U.S., as is J.K. Rowling's Harry Potter and the Half-Blood Prince.

Comprising of a lengthy 672 pages, the novel is likely to keep the film's target audience away from cinemas for the entirity of the Warner Bros. film's opening week.