London, Nov 8 - Actress Michelle Williams says she always finds working on film sets a little difficult.

The Oscar-nominated actress has taken on her biggest role till date as Marilyn Monroe in "My Week with Marilyn", reports femalefirst. co. uk.

"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," she said. (IANS)