Mila Kunis found her love scene with Natalie Portman on 'Black Swan' "uncomfortable".

The Ukrainian-born actress - who stars opposite Portman in the Darren Aronosky-directed project - had trouble shooting the intimate scene with the 29-year-old beauty because they are friends, but she believes the storyline is important for the film.

She said: "It is slightly uncomfortable to have to be intimate with a good friend. The scene's important for the character, but we went in going, 'This is going to be a little different,' yeah."

The 27-year-old star believes Lily - the ballet dancer she portrays in the film - is an unusual character, and she was unsure as to how the film would be cut by Aronofsky and it would be seen at the end.

She said: "She's the strangest character I've ever played.

"We shot everything both ways. Sometimes I would be the sweet one and Natalie would be the mean one, and then we'd flip it. At the end of the day it was all up to Darren."