Will Smith was to present an award
Actor Will Smith has become the first celebrity to pull out of the Academy Awards on Sunday following the start of military action in Iraq.
TV coverage of the event is still uncertain with US network ABC admitting it will wait until Friday before deciding on its broadcast plans.
The organisers of the Academy Awards have said the ceremony will be a less glitzy affair to reflect the war in Iraq.
The glamorous red carpet arrivals have been dropped, prompting a mixed reaction from Hollywood.
"I really was stunned and very disappointed. We've let Saddam Hussein push us around one more time," said Johnny Grant, Hollywood's honorary mayor.
But star Arnold Schwarzenegger, known for his hardman roles, said the move made sense. "I think it's a good idea to try to eliminate the red carpet and also try to eliminate all the political speeches."
Smith's publicist, Stan Rosenfield, said the star "felt uncomfortable in attending and respectfully asked to be excused".
"There's no agenda, there's no speeches. He just felt uncomfortable in attending."
There will also be no seats for fans outside the Kodak Theatre, in Los Angeles, one of the traditional elements of the Oscars.
Zeta Jones is due to give birth two weeks after the Oscars
ABC network has said it may break from the Oscars to give viewers news updates or provide up-to-date information at the bottom of the screen.
Bryce Zebel, producer of the Emmys, cancelled on the day bombing started in Afghanistan after 11 September, said: "It's going to be very difficult juxtaposing images of a nation at war with images of an awards show."
Meanwhile, Chicago co-stars Catherine Zeta Jones and Queen Latifah are to perform a duet at the toned-down Oscar ceremony.
Zeta Jones will take to the stage on Sunday to sing a song from the movie despite being eight months pregnant.
Both Latifah and Zeta Jones have been nominated for an Oscar in the best supporting category, for their performances in Chicago.
Zeta Jones is due to give birth to her second child with husband Michael Douglas two weeks after the Oscars.
It is expected that an ambulance will be on standby outside the Kodak Theatre in Los Angeles in case the baby arrives early.
And a dress destined for Angelina Jolie to wear at the Oscars has been stolen from a British designer's car in London.
Scott Henshall said: "There is no way I can remake Angelina's or any other dresses in time."
The awards themselves, which seem increasingly irrelevant, are likely to be dominated by the musical Chicago - which is a firm favourite to take best picture. Britain's best hopes are Daniel Day Lewis (Gangs of New York) and Zeta Jones.
A press conference will be held on Friday to announce any changes to the schedule.