Iranian actresses Sareh Bayat and Sarina Farhadi (R) of the film 'Jodaeiye Nadar Az Simin' ('Nadar and Simin, A Separation') pose with their Silver Bear award for Best Actress after the awards ceremony at the 61st Berlinale International Film Festival in Berlin February February 19, 2011. [Photo/Agencies]

Director Asghar Farhadi (R) poses with the Golden Bear award for Best Film together with actress Sarina Farhadi, who won the Silver Bear award for Best Actress, during the awards ceremony at the 61st Berlinale International Film Festival in Berlin February 19, 2011.[Photo/Agencies]

Iranian drama "Nader and Simin: A Separation" is the title to beat as this year's Berlin film festival heads toward the closing ceremony on Saturday where the coveted Golden Bear for best picture is handed out.

A subtle and gripping examination of Iran's social divide, religious traditions and justice system, Asghar Farhadi's portrayal of the break-up of a marriage has won almost universal praise from critics at the annual cinema showcase.

What critics say and judges decide often differ, however, making it an unpredictable event often full of surprises.

In Nader and Simin, one family is pitted against another in a gripping legal tussle which Farhadi said underscored the gap between middle class "intellectuals" and poorer, traditional Iranians whose religious beliefs tended to be more entrenched.

"One (undercurrent in Iranian society) is the struggle between the classes -- between the poor, who are more traditional and religious, and the other class which wants to live according to modern rules," he said in Berlin.

"It's a somewhat hidden struggle between the old and new in our society. It will cost our society dear."

While many of the 16 films in the main competition line-up were seen as forgettable, it only takes one or two strong contenders to light up a festival like Berlin, and Nader and Simin provided that spark.

It also fits in neatly with what some German media have dubbed an "Iranian Berlinale," after the festival opened with calls for Iran to allow director Jafar Panahi to travel to Berlin and accept his invitation to sit on the jury.

EMPTY CHAIR

Panahi was sentenced to six years in jail and banned from making movies or traveling abroad for 20 years after being accused of inciting opposition protests in 2009 and making a film without permission.

His absence was marked with an empty chair alongside jury head Isabella Rossellini at the opening press conference.

Potential Golden Bear rivals are "The Forgiveness of Blood," about Albania's ancient blood feuds, "If Not Us, Who" about the rise of violent German leftist groups in the 60s, and Hungarian director Bela Tarr's strange and stark "The Turin Horse."

His self-declared last picture is a black-and-white portrayal of the seemingly endless repetition of daily life for a poor farmer and his daughter -- drawing water from a well, eating potatoes, stoking the fire, dressing and sleeping.

British actor Ralph Fiennes's directorial debut "Coriolanus," a bloody adaptation of the Shakespeare tragedy set in modern times, won plenty of fans at the festival.

The Hollywood Reporter tipped Fiennes in the title role and Vanessa Redgrave as his mother Volumnia as possible best actor and actress winners respectively.

Acting honors could also go to Kevin Spacey as a banker facing a moral dilemma on the eve of the 2008 financial crash in "Margin Call," to the young cast of The Forgiveness of Blood or to the leads in If Not Us, Who, the trade newspaper added.