Washington, Nov 7 Michelle Williams has revealed that she always finds working on film sets difficult to a "degree".

The 31-year-old Oscar-nominated actress who is playing Marilyn Monroe in `My Week with Marilyn' admits that although she is always nervous, but taking on this role really "stepped it up".

"It is the most challenging role I've taken, and I think it always will be. There is a degree of difficulty that always exists for me at work, but this really stepped it up. I was nervous, of course, but I tried not to think of her as an icon," Contact music quoted her as telling Culture magazine.

"She most yearned to play dramatic roles, but I really rather take to her comedy - and in `The Prince and The Showgirl' there's some work that she's never bettered," she added.

Michelle had also admitted previously that she was too scared to take on the role and even had to have her passport taken away in case she tried to get on a plane to escape.

"I was so scared. Making this film felt like being in free fall. I think after the second day, I told them they had to take away my passport because I was a flight risk - I wanted to hop on the next train to the Alps or something and get the hell out because it was terrifying," she added. (ANI)