Sienna Miller is the first actor to enlist in Paramount Pictures' big-budget tentpole G.I. Joe, reports Variety.
The British actress will play the film's female lead, described as a raven-haired baroness and sexy femme fatale skilled in espionage.
Stephen Sommers directs the live-action film based on the Hasbro toys, comic book and TV series.
Paramount, which has set a mid-February start date, has slotted the film for an August 7, 2009, release.
The story is set at Brussels-based GIJOE, an acronym for the Global Integrated Joint Operating Entity, and revolves around an international co-ed force of operatives who use high-tech equipment to battle Cobra, an evil org headed by a Scottish arms dealer.
Lorenzo di Bonaventura (Transformers) is producing alongside Hasbro's Brian Goldner.
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