Naomi Watts doesn't know how to play Marilyn Monroe in biopic

English-Australian actress Naomi Watts has admitted being daunted by the prospect of playing Marilyn Monroe in the new movie Blonde.

The 42-year-old is set to play the role of Monroe in a biopic and isn't sure where to start.

"I don't have a plan yet on how to do it, it's going to be a huge undertaking because everyone obviously has their own idea about who she was," the Daily Express quoted Watts as saying.

"It's a high-pressure thing to take on because of how iconic she was."

"I don't know how I'll go about it," Watts said.