Sienna Miller is enjoying "kicking butt" in her new movie.

The British actress is reveling in the role of gun-toting villain The Baroness in upcoming blockbuster 'G.I. Joe'.

She said: "It is really fun, and I get to really kick some butt."

"I am working out a lot and kick boxing and all that. But the best bit is that I'm doing that gun-twisting stuff. I am learning how to shoot properly and it's all cool and a lot of fun."

The Baroness has been described by film sources as a "raven-haired, sexy femme fatale skilled in espionage", and appeared in the first ever issue of the 'G.I. Joe: A Real American Hero' comic in 1982.

The movie follows the escapades of the elite 'G.I. Joe' team who take on an evil organization run by a notorious arms dealer. The cast also includes Dennis Quaid, Joseph Gordon-Levitt, Channing Tatum, and Marlon Wayans.

'G.I. Joe' - inspired by a famous 60s toy action figure which spawned the comic book series - is due to hit screens in August 2009.