When "Seeking a Friend for the End of the World," you're probably going to look for one with a few "benefits."

At least, that's how it plays out in Lorene Scafaria's film, which stars Keira Knightley as Penny and Steve Carell as Dodge, two neighbors who find themselves striking up an intimate relationship when faced with the doomsday scenario of an asteroid headed for Earth.

That relationship, at first, isn't really romantic, Knightley has explained.

"I don't know that their romantic arc actually has much to do with romance in the beginning and more to do with 'It's the end of the world, and we both want to have sex,' " the "Pride and Prejudice" actress told MTV.

"I think that was sort of more what the romantic arc was hinged on, and then what it becomes is about friendship," she continued of the two characters, who don't speak to each other until they're forced to - you know, because the world's about to end.

Not that the recently engaged actress had any trouble generating chemistry with Carell.

"As far as chemistry goes with Steve, he is one of the loveliest men in the entire world," she said. "He is so funny, and so courteous to everyone. He is a consummate professional. He's just a lovely, lovely man. I defy anybody not to have good chemistry with him."

The apocalyptic comedy opens this weekend.