The Oscar-winning actress is sitting on this year's (13) judging panel alongside the likes of Christoph Waltz and Ang Lee to decide which movie will win the prestigious Palme d'Or trophy.
And Spielberg is ensuring his jury members are not swayed by outside opinion by banning them from chatting publicly about the festival's hottest films.
Kidman tells Britain's Daily Mail, "Look, Steven's been very clear about us not commenting on the films that are in competition. He said, 'Just say No comment when people start asking you.' He was very strict about it and I'm not going to get into trouble with Steven!
"I think Steven's right: it's not fair to the competition film-makers. I have to say I'm looking forward to the debate we will all have when we have to decide on the Palme d'Or."