Every time I'd see him, I'd start observing him like a hawk, says Ranbir on playing Sanjay Dutt!

Now that Jagga Jasoos has now released, Ranbir Kapoor's complete focus will now be on the Sanjay Dutt biopic which is being directed by Rajkumar Hirani. The film is backed by a stellar cast comprising of Paresh Rawal, Manisha Koirala, Sonam Kapoor, Dia Mirza, Anushka Sharma, Vicky Kaushal and Karishma Tanna.

Ranbir's uncanny resemblance to Sanjay created a positive havoc on social media. On this, Ranbir got candid with a leading tabloid and told, "Yeah! We worked really hard at it, doing four months of prosthetic (make-up) trials, lots of disappointments, thinking that it's not going to work out. But you need to put in that time and effort. It's a daunting task to play someone like Sanjay Dutt, who everybody knows anyway."

Just like everyone else, Sanjay too was surprised by Ranbir's transformation. Ranbir told, "It was surreal for me. You're acting like him, and the director calls cut, you look up, and suddenly there's Sanjay Dutt actually sitting behind the monitor! But then I'd got so obsessed with him. Every time I'd see him, I'd start observing him like a hawk — the way he scratches his beard, twitches his eye, drinks water, hugs… It'd become a bit of a sickness for me. But that obsession is necessary for acting, or any form of art — that madness to get something right. You may still fall flat on your face, but it's necessary."

The Sanjay Dutt biopic is slated for a March 2018 release. Ranbir is presently in New York to shoot for an important sequence in Sanjay Dutt's life when he was in rehab to deal with his drug addiction.