An offer is in place and talks are ongoing though a deal is yet to be made, reported the Wrap.
Rocket is enjoying a rare spotlight in decades after Disney decided to make a film.
The trigger-happy woodland creature's look was revealed in sizzle-reel footage shown at Comic-Con.
Cooper could be the latest A-lister to join the film after it emerged that Vin Diesel will voice the jiant tree-like creature Groot.
Introduced in 1969, the Guardians of the Galaxy are an Avengers-like superhero team from the 31st Century who exist in an alternate time-line from the Marvel Universe.