The fifth installment in the wildly successful series of novels about the teen-age wizard and his friends had been expected to fly into stores this summer, but a spokeswoman for J.K. Rowling said Thursday that the author is unlikely to finish writing before the end of the year.
Rowling is still working on "Harry Potter and the Order of the Phoenix," and it might not be published until 2003, spokeswoman Rebecca Salt said.
"It could be this year and it could be next year," Salt said.
She denied there had ever been a specific deadline and rejected any suggestion that Rowling was suffering from writer's block.
However, Rosamund Delahey, a spokeswoman for Bloomsbury publishers, said the next book still could hit the shelves later this year. Delahey said a British publication date will be announced as soon as Rowling provides a finished manuscript.
"J.K. Rowling is happily writing a new book, and we anticipate publishing later this year," she said.
Meanwhile, Judy Corman - spokeswoman for New York-based Scholastic, which publishes the Potter books in the United States - said she expects the fifth installment to come out during its 2003 fiscal year, which begins in June 2002.
"There is a process, once we get it in house, of editing, designing the cover and getting it on the printing presses," Corman said. "I understand her fans are eager, as we are, but J.K. Rowling writes substantial books, and they are not turned out as small novellas. Her last book was over 740 pages."
Bookshops around Britain have been inundated with calls from people eager to find out when they can get their hands on the next book.
Potter fans are used to snapping up the novels in the summer since the previous ones have been published in July.
The first, "Harry Potter and the Philosopher's Stone," published in the United States as "Harry Potter and the Sorcerer's Stone," came out in 1997. The next three followed at the rate of one a year.
There was no book last year, but fans were treated instead to the film version of the first installment.
Rowling has promised to write a total of seven books, one for each year that Harry spends at Hogwarts School. The series chronicles the boy's adventures at a boarding school for wizards as he battles his nemesis, the evil sorcerer Voldemort.
Britain is gearing up for another bout of Pottermania with Friday's video and DVD release of the Potter movie. Experts predict it will be the biggest seller of all time, smashing the previous record held by "Titanic."