Director Roman Polanski reacts after winning the Best Director award for his film "The Ghost Writer" during the 36th Cesar Awards ceremony in Paris February 25, 2011.[Photo/Agencies]

Twenty-one films will vie for the top Golden Lion award at the 68th edition of the world's oldest film festival, which runs from Aug 31 to Sept 10 this year on the Lido seafront.

Madonna's directorial debut on a feature film, "W.E", is a drama that compares a modern day relationship with the controversial love between the king and divorced American Wallis Simpson, and will screen out of competition.

The king abdicated in 1936 in order to marry Simpson.

French-Polish director Polanski's latest film is an adaptation of Yasmina Reza's hit play "God of Carnage" and stars Kate Winslet and Jodie Foster.

Other highlights include Tomas Alfredson's adaptation of John Le Carre's Cold War thriller "Tinker, Tailor, Soldier, Spy" and David Cronenberg's hotly anticipated psychological drama "A Dangerous Method" starring Keira Knightley and Viggo Mortensen.

British director Andrea Arnold's remake of Emily Bronte's "Wuthering Heights" and Ami Canaan Mann's "Texas Killing Fields" starring Sam Worthington, also feature in the lineup for the festival, which often serves as a launching pad for the Oscars.

Organizers earlier announced that George Clooney's "The Ides of March" about the U.S. presidential race set in the near future would open the festival.

The Hollywood star, a regular on the red carpet in Venice, wrote and directed the political drama, which is based on Beau Willimon's play "Farragut North".