The sixth instalment was 2005's best-selling book in the US

Publisher Scholastic said July's release of Harry Potter and the Deathly Hallows would be supported by a multi-million dollar marketing drive.

"It's a true celebration of the Harry Potter movement and of the joy of reading," said spokeswoman Lisa Holton.

The six previous books about the boy wizard have sold 325m copies worldwide and spawned four hit films to date.

Reviving

Author JK Rowling has earned an estimated �520m from her creation, after writing the first book while a single mother on benefits.

The final instalment will be published 10 years after the first.

The writer had always planned seven books, each following the characters for one school year at the Hogwarts School of Witchcraft and Wizardry.

Rowling has revealed that two characters die in the final book, prompting bookmakers to take bets on whether Potter could be one of them.

The books have been credited with bringing children back to reading and the movie adaptations with reviving the British film industry.

The fifth film, Harry Potter and the Order of the Phoenix, will be released just days before the book.