CANNES • There is a killer moment in the new film Pope Francis - A Man Of His Word when you realise what he is up against.

The Argentine is dressing down the cardinals and bejewelled princes of the Curia who run the Catholic Church, lacerating them for their greed, back-stabbing and lust for power.

The scandal-hit, Italian-dominated body is full of people leading immoral double lives who "possess a heart of stone and a stiff neck", he tells them in German director Wim Wenders' remarkable insight into the leader of the world's 1.2 billion Catholics.

"Pay a visit to the cemeteries" and look at those "who thought they were immortal, immune and indispensable", Pope Francis urges them in the feature, which premiered on Sunday at the Cannes film festival.

"You see the sharp faces of some of these cardinals who are rich and ambitious," said Wenders, who interviewed the pontiff over several months for the portrait.

"But you can also see other archbishops thinking: 'Yes, this is why we elected you.'"

Wenders, who won the Palme d'Or for Paris, Texas in 1984, has made several successful documentaries, including Buena Vista Social Club (1999), about the Cuban music scene; and Pina (2011), on dance choreographer Pina Bausch - subjects that, like the Pope, he has great affection for.

"My documentaries are expressions of love and affection for something that I want to share with the world.

"Right now, I think there is nobody who has more important things to say to us than the Pope, so I wanted to share that.

"We are living in an utterly immoral time and our political leaders, powerful leaders, are emotional dwarfs. So, I wanted to have this emotional giant talk to us."

Jorge Mario Bergoglio, born in Argentina in 1936, became the Pope in 2013 after the unexpected resignation of Pope Benedict.

He chose his papal name after Francis of Assisi, a figure Wenders calls "a revolutionary" for his work with the poor and nature.

"Today, Saint Francis would be the first ecologist of the world. Pope Francis took on a heavy duty by choosing that name," Wenders said.

He filmed four two-hour interviews with Pope Francis, in which the latter talked directly into the camera.

The film-maker said a kind of "teleprompter in reverse" allowed him to get that intimate look, by imposing Wenders' face on a transparent screen with a camera behind it "so by looking into my eyes, he sees everybody's eyes".

"This man communicates in such an honest, direct and spontaneous way... even with the greatest actors, you find that very rarely," Wenders said.

The director said the Vatican contacted him to ask whether he would be interested in talking to the Pope.

"I was given carte blanche," he said, adding that he had access to the Vatican's video archives.

"There was no interference whatsoever," he insisted, despite the film being co-produced by Vatican television.

Wenders insists his film is more than a promotional video. "It is not propaganda," he said.

"It's not a commission. I was free to do what I wanted to do and this is what I wanted to do. I wanted to give a platform for his work, period."

Wenders said he was also touched by the Pope's deep tolerance of other religions and lifestyles.

"He says don't try to convert anybody. Just try to convince them to be of good will and to accept one another. His firm belief is there is no difference between people."

But despite trying to lead by example by living modestly, the Pope knows his power is limited.

"All he has are his words," Wenders said. "Each time he left us after the shoot, he would look into our eyes and ask each of us: 'Please pray for me.'

"There are a lot of people praying for him, praying that he can do it," Wenders said.

REUTERS, AGENCE FRANCE-PRESSE