Fanning, the rising star and younger sister of Dakota Fanning, auditioned for the role at the age of 12 and adopts an accomplished British accent to play politically aware Londoner Ginger in "Ginger & Rosa," which screened Monday at the New York Film Festival.

"Orlando" filmmaker Potter, 63, told a news conference that while the film features various U.S. actors including Annette Bening and Oliver Platt, she did not set out to cast Americans Fanning and Alessandro Nivola in the central roles of Ginger and her charming, pacifist father.

She was searching for an unknown young English actress and scanned more than 2,000 such leads before coming across Fanning, who started acting just before age 3 and who recently caught attention in "Super 8" and other films.

A giggling Fanning told reporters her blonde hair was dyed red, befitting the name of her nuclear bomb-protesting and poet title character, for the film that explores adolescence, family discord and political and moral contradictions.

"I was very nervous," Fanning, now 14, said of the initial audition, noting that since Potter is British, "I was worried she was going to be judging me on my accent." But soon, such was their camaraderie, she said with excitement, "I felt like we were, sort of, a part of each other in a way."

The movie, which is winning glowing reviews after debuting at the Telluride and Toronto film festivals, has been hailed as a return to form for Potter since she first gained acclaim in 1992 for "Orlando," based on Virginia Woolf's novel that helped build the career of actress Tilda Swinton.

" 'Ginger & Rosa' is a miracle of wing-clipping, which launches Potter back into the mainstream for the first time since 'Orlando'," said the Guardian, giving the film four out of five stars, while the Hollywood Reporter said Fanning's performance was "simply extraordinary."

The film opens with an image of the atomic bomb dropped on Hiroshima before quickly turning to early 1960s London and the bond between the curious Ginger and her darker, sexually adventurous best friend, Rosa, played by Alice Englert.

Ginger is encouraged by her writer father - who is not bound by traditional fatherly stereotypes and insists on being called by his first name, Roland - in her penchant for activism, but Rosa soon finds adulthood encroaching as her parents split and Rosa develops a crush on Roland.

Besides offering a rare look at a story centered on a bond between young women, Potter said the film also explores the moral chasm between politics and personal conduct that sometimes existed among that era's political liberals.

"It may be a universal theme of contradictions within a character," she said, "but there may also be on another level, if I am honest about it, a kind of auto critique, let's say, of the left. If we don't look honestly at where we have gone wrong, we are never going to move forward."

"It was certainly my observation of the period that you could be a man, or a woman ... of really radical, free-thinking, humanitarian, forward-thinking, courageous ideas - and yet flawed in the sense of an ethical, moral, gray area where it was possible to be sort of blind," she said.

Potter, who also wrote the script, said that in the early 1960s she was only slightly younger than the girls in the film and "like any writer, I scavenged mercilessly in my own life and my own memories" as well as her own imagination to write the tale.

"I certainly remember the Cuban missile crisis," she said, "and what that felt like, the feeling that the world could end, like tomorrow morning ... it's not the '60s of peace and love and flowers in your hair and sexual revolution."

(Editing by Jill Serjeant and Matthew Lewis)

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