"The producer, Miramax, said that they still had to complete technical modifications...and it won't be ready in time," a spokeswoman for the festival said.

The Hours casts Kidman in the role of Virginia Woolf, and also stars Julianne Moore and Meryl Streep.

Kidman has had a string of successful films in the year since she divorced actor Tom Cruise, such as Moulin Rouge and The Others. But her most recent movie Birthday Girl, in which she played a mail-order bride, received mixed reviews.

The Hours, theatre director Stephen Daldry's first since his only other movie, critically acclaimed hit Billy Elliot, was to have been in competition for the prestigious Golden Lion.

It focuses on three women in different eras profoundly affected by the writer's works.

Considered an early front-runner for the Oscars, it was to compete against films including Sam Mendes' latest movie Road to Perdition, starring Tom Hanks, and Stephen Frears' Dirty Pretty Things.

Vacant slot

Moore had been set to promote The Hours at the festival. Todd Haynes' Far From Heaven, also starring Moore, will now fill the vacant competition slot.

The film is about an American housewife living in racially charged suburban Connecticut in the 1950s who finds her husband in bed with another man.

Festival organisers also said Adoor Gopalakrishnan's Nizhalkkuthu would now compete in the Upstream section -- devoted to first full-length films at the cinematic fringes.

Ridha Behi's La Boite Magique and Aurelio Grimaldi's Rosa Funzeca are late additions to the programme.

Stars such as Hanks, Salma Hayek and Sophia Loren are among those expected to attend the 59th Venice festival when it opens on 29 August.

It will be Loren's first visit to the Venice festival for 20 years.

The festival kicks off this year with Frida, which stars Hayek as surrealist Mexican artist Frida Kahlo.

Directed by Broadway veteran Julie Taymor, the film co-stars Edward Norton, Ashley Judd, Geoffrey Rush and Alfred Molina as Kahlo's husband Diego Rivera.

Countries represented at the festival include South Korea, Italy, France, Russia and Japan.