Britney's big screen premiere

Singer Britney Spears has turned actress with the premiere of her first film, Crossroads.

The 20-year-old sported a trendy 70s-style cap and a pink dress at the event last night in Los Angeles, which she attended with her boyfriend Justin Timberlake, of N'Sync.

Spears was confident her film debut will not be a Mariah Carey-style flop.

She is the first singer to make a big screen debut since Carey's film Glitter, which became a laughing stock with critics and made a massive loss at the box office.

Spears said she was confident her film would be a success.

"It wasn't easy for me. The whole transition was a little scary at first, but I'm so happy I did it.

"I'm very, very happy with the movie, so we'll see what happens. I'll be curious to see.

"I'm ambitious and I like to challenge myself and I like to push myself and so it made me want to really go there just to see if I could do it. Just to see.

"But it's not even so much about it being the biggest movie in the world, as long as my fans can go to it and be touched by it in its own way."

Spears stars as an American teenager who ends her time at school by taking a trip to Los Angeles with her boyfriend Ben, played by Anson Mount, and two childhood friends, played by Taryn Manning and Zoe Saldana.

The group go in search of Spears' character's mother, played by British-born actress Kim Cattrall, who plays Samantha in Sex and the City.

During the film, her character loses her virginity off-camera, prompting the rating which is designed to keep away Britney's younger fans.

"Actually, the writer came up with that," she said. "It was in the script. It totally fitted. I thought it was necessary for the character. I thought it made sense."

And she admitted some of the content might cause concern for parents taking children to the film.

"I think that it's up to the parent to decide. My sister's 10-years-old and she went to go see the movie and she loved it."