Naomi felt 'pressure' portraying Diana

Los Angeles - Naomi Watts felt "pressure" about playing Princess Diana.

The 44-year-old actress has just finished shooting upcoming biopic Diana about the late British royal's life, but admits she originally tried to turn down the role as she felt scared of what people's reactions would be to her portraying such a popular figure.

Speaking on The Ellen DeGeneres show, Naomi admitted: "I tried to say no. But I guess every time I said no, I rang back up and said, 'Oh, I changed my mind.'

"I think just the pressure, because we all feel we know her so well. The pressure of that is scary, because everybody thinks, 'Oh, you're not the right look or whatever'."

Difficult to portray Diana

After previously confessing she was "dreading" starring in the film, once she started to play the part Naomi found the princess had a "great sense of humour".

"She was kind of a rebel, in a really kind of good way," Naomi added.

The actress - who has just received a Golden Globe Best Actress nomination for The Impossible - recently revealed she wanted to do justice to the beloved mother of Princes William and Harry, and tried to stay true to her story.

"It's very difficult to play someone who had such a deep impact and left such a lasting memory on the public," she explained.

"Our memory of her is still very fresh and you have to be respectful of that. It's also more complicated and sensitive when you take into account her two sons. But I want to do her justice and tell her story truthfully."