Pattinson, Penn circling 'Elephants'

Robert Pattinson and Sean Penn are in talks to star in drama Water for Elephants.

The actors could join the already cast Reese Witherspoon in the film based on the 2006 bestseller by Sara Gruen.

The plot features a circus employee love triangle set in Depression-era America.

Twilight star Pattinson would play a veterinary student who falls in love with the circus' equestrian rider (Reese). Penn is expected to take on the role of her husband, a dangerous animal trainer.

I Am Legend helmer Francis Lawrence has signed to direct.