The release of the new Harry Potter film, Harry Potter and the Half-Blood Prince has been delayed to cash in on the summer blockbuster season.

The film was originally set for release this November, but will now not be screened in the US, until July 17th.

The move will mean a two-year delay between the film adaptations of books five and six in JK Rowling's fantasy series.

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Actors Jim Broadbent and Daniel Radcliffe in a scene from film Harry Potter and the Half-Blood Prince. The movie has been pushed back to next summer

Daniel Radcliffe, Emma Watson, right and Rupert Grint, left, are all reprising their roles in the latest instalment of the Harry Potter books

JK, who has homes in Perthshire, London and Edinburgh, has already made an estimated £560m fortune from the Boy Wizard series, films and merchandise.

But the delay over the latest movie will shorten fans' wait between Half-Blood Prince and the final two instalments of Harry Potter and the Deathly Hallows, which are being shot simultaneously next year.

It is thought actors Daniel Radcliffe, Rupert Grint and Emma Watson - who is celebrating getting straight As in her A Levels in English Literature, Geography and Art - will reprise their roles.

The release date for part one is tentatively set for November 2010.

The sixth instalment of the teenage wizard's adventures was supposed to have its Royal premiere on November 17.

Warner Brothers blamed the writers strike for the impact on their film releases

Alan Horn, president of studio Warner Bros, said the decision was taken to guarantee the studio a major summer blockbuster in 2009.

He said: :There is no production delay or production consideration. . . . It feels like we have an opportunity in the summer."

He also blamed the Hollywood writers' strike, which hit the film industry hard earlier this year.

Mr Horn said the strike, which ended in February, had "impacted the readiness of scripts for other films." 

"The picture is completely, absolutely, 100 per cent on schedule, on time. There were no delays," he said.

But Horn acknowledged that the studio would have to pacify fans in the months to come.

"We would never do anything to hurt one of the movies or the series. We love our fans."

"Half-Blood Prince" finds Harry (Daniel Radcliffe) returning to his wizard classes with a clandestine assignment to root out dark secrets about the early years of his archenemy, the dark Lord Voldemort.

The film is directed by David Yates, who made the fifth movie and also is shooting the final two.

Last February, another big Hollywood film, Paramount's "Star Trek," was bumped from a December release to May 8, 2009. Paramount executives said that move also was intended to take advantage of an open weekend in the summer line-up.