Rachel Weisz and Emily Blunt are to play sisters in a new semi-improvised project.

The as-yet-untitled movie - which is to be filmed in Seattle later this month - is to be produced by Steven Schardt, and is expected to take just a couple of weeks to shoot.

Indie director, writer and producer of the film Lynn Shelton has recruited the two British stars to play a pair of siblings who find their relationship is put to the test when a man - played by 'Humpday' actor Mark Duplass - threatens to come between them.

Both actresses are well-known for having notoriously busy work schedules, with Weisz having spent a week on Terrence Malick's untitled new film earlier in the month, while shooting for 'The Deep Blue Sea' begins in November.

It is thought the brief shoot time of the Lynn Shelton film is what has allowed Weisz to take part, as she will be able to Squeeze it in prior to 'The Deep Blue Sea'

Meanwhile, Blunt recently signed up to star in Rian Johnson's new sci-fi tale 'Looper' opposite action movie legends Bruce Willis and Joseph Gordon-Levitt.