Sandra Bullock in Negotiations to Star in 'Gravity'

LOS ANGELES - Sandra Bullock is in negotiations to star in "Gravity," the outer-space thriller that has become a game of musical chairs for the in-demand actress set.

Alfonso Cuaron ("Children of Men," "Y tu mama tambien"), who is directing and co-wrote the script with his son Jonas, is readying the feature for Warner Bros. It will co-star Robert Downey Jr.

The studio went to Bullock after Natalie Portman's on-and-off-again negotiations went into off mode for good.

"Gravity" has a dizzying history when it comes to attracting female stars.

The project originally was set up at Universal as a vehicle for Angelina Jolie, but it moved to Warner Bros., where it hit several bumps: Jolie left the project, partially because of the studio's balking at paying her $20 million fee. Although Downey brings star power to the project, his role is overshadowed by the female lead, an astronaut whose struggle to survive an avalanche of space junk becomes the movie's focus.

In the summer, the studio talked to Marion Cotillard, then tested Scarlett Johansson and Blake Lively for the part before re-engaging Jolie. After that skidded out, the studio began talks with Portman, who had just started generating heat from her performance in "Black Swan."

Bullock is also in talks to star in "Extremely Loud and Incredibly Close," an adaptation of the Jonathan Safran Foer novel that would star Tom Hanks.