Natalie Portman has passed on the chance to take a leading role in 'Gravity'.

The 'Black Swan' actress is the latest star to pass on the movie, following Angelina Jolie deciding it wasn't for her in September.

According to, scheduling conflicts the reason behind Portman giving up the opportunity, and Warner Bros is now attempting to get Sandra Bullock on board to play the leading character.

The movie tells the tale of a female astronaut who must make her way back to earth following an explosion on her space station.

Robert Downey Jr. is still signed up for the male role in the Alfonso Cuaron-directed $80 million project.

Other actresses previously considered for the leading role included Naomi Watts, Sienna Miller and Blake Lively.

Portman's performance in Darren Aronofsky's 'Black Swan' has led to rumours of an Oscar-nomination for the 29-year-old beauty.

She will next appear as Jane Foster in 2011 movie 'Thor'.