"I still don't know what he will prefer: the action film, which is more similar to his own cinema, or the auteur film that is completely different," said Fremaux, who has overseen the festival since 2001.
Spielberg did drop a hint, however. Fremaux said Spielberg told him that on the jury "I want to make a journey. I want to know how people make cinema in a different way than mine".
Spielberg is joined on the jury by actors Nicole Kidman and Christoph Waltz, and director Ang Lee.
The 20 contenders for the Palme d'Or include new movies from the Coen brothers, Roman Polanski, Alexander Payne and Asghar Farhadi.
It's notoriously difficult to predict the winner, but some things at Cannes are guaranteed. There will be sand. There will be sun - despite a forecast of rain for the opening night. And, Fremaux says, there will be sex.
Asked if there's a theme running through the selection, Fremaux suggested "love, the main theme of history".
Films with a romantic element include Steven Soderbergh's Liberace biopic Behind the Candelabra, Abdellatif Kechiche's coming-of-age story La Vie d'Adele and possibly Farhadi's post-divorce tale The Past.
Fremaux said some of the movies push boundaries in terms of the screen depiction of sex - even though times have changed since a film called La Grande Bouffe scandalised Cannes in 1973 with its graphic sex and nudity.
No longer quite so shocking, La Grande Bouffe is being screened again this year as part of the Cannes Classics programme.
"I think society is much more open than 40 years ago and it's more possible to talk about sexuality," Fremaux said.
"Directors have got freedom to do what they want to do. [But] that freedom goes maybe to certain limits so we will see."
- AP
