New Delhi, Dec 1 (IANS): National Award winning actress Priyanka Chopra, who earlier called "Mary Kom" her toughest film ever, says her new film "Bajirao Mastani", a period drama, is testing her acting skills too.

Sanjay Leela Bhansali's “Bajirao Mastani” marks actress Priyanka's first period film.

“It's my first period film and it is very difficult to do a period film which narrates a story about an incident that happened about 500 years ago, with no reference. The role is tremendously hard,” the actress told IANS.

The film is based on the love story between Maratha Peshwa Baji Rao I (Ranveer Singh) and his second wife Mastani (Deepika Padukone). Priyanka plays Kashibai, the first wife of Baji Rao.

“The role is probably one of the most difficult that I have done till now. It's because it is based in the era where I need to be correct in the period and the culture. The role is heart-breaking as well. It's testing me as an actor,” Priyanka said.

Priyanka, who was in the capital to unveil the Girl Rising campaign in India recently, expressed her desire to revisit a negative role a la the sex-deprived boss she essayed in "Aitraaz".

“I so want to do a negative role as they are very different from real you. You can be whatever you want and evil,” the actress said.

“As of now I'm not doing anything negative. But I'm looking at few things...let us see,” the actress added.