The heartthrob has never appeared in an action film before and is expected to become physically fit for the role.
Director Milan Luthria told The Times of India: "I am always excited by unusual casting and this is very unlike anything Imran has played before. It is unexpected for audiences. It's a character with a mass appeal with great one-liners, in keeping with the first part of the franchise.
"I sense Imran is an extremely committed actor, and am sure he will go the distance to achieve the look I have in mind, which requires a strict dietary regimen and extended endurance training among others.
"I am awaiting Imran's return from Chandigarh to discuss this at length with him. Meanwhile we've been in touch over the phone and email."
In January, Khan denied that he goes for controversial roles in order to shock audiences.
He said more recently that celebrity infighting is deliberately kept away from the media.