The `Lost in Translation` actress and the `Gossip Girl` beauty are both vying for the main female part in sci-fi movie `Gravity`, which tells the tale of a female astronaut who gets lost in space.
It had been thought Scarlett had "verbally agreed" to star opposite her `Iron Man 2` co-star Robert Downey Jr. but Blake is now being considered for the part.
The film - which is being directed by Alfonso Cuaron - is being dubbed a contemporary survival thriller, and will be at least 60 per cent CGI (computer-generated imagery). It will also feature an ambitious opening 20-minute sequence.
As well as `Gravity`, it was recently revealed Scarlett is being lined up to play Vince Vaughn`s lover in a new film.
The 25-year-old actress is reportedly in talks to appear in `Old St. Louis` as a secretary who is secretly romancing a travelling salesman.
In the comedy drama, Vince`s divorced businessman character tries to combine his latest cross-country work trip with an attempt to reconcile with the teenage daughter he rarely sees.
However, it is thought Scarlett won-t be able to do both films, as they are slated to begin production in October.