Cumberbatch has long been linked to a role in Star Wars: Episode Vii, which would reunite him with his Star Trek Into Darkness director J.J. Abrams, but the Sherlock star claims the project is no longer on his radar.
He says, "I would've liked a part in J.J.'s new Star Wars but it won't happen, sadly."
Cumberbatch has not elaborated on the reasons for the failed deal.
Details about the new cast have been kept tightly under wraps, although unknown actress Maisie Richardson-Sellers is among the frontrunners for a leading role, alongside Breaking Bad's Jesse Plemons and other acting newcomers John Boyega, Ed Speleers and Matthew James Thomas.
Michael B. Jordan, Saoirse Ronan and Oscar winner Lupita Nyong'o have also met with Abrams to discuss possible parts, and Girls regular Adam Driver is said to have landed the role of lead villain.
The only confirmed castmembers so far are original trilogy stars Peter Mayhew, who will reprise his role as Chewbacca, and Carrie Fisher, who will return as Princess Leia.
The latest Star Wars epic recently began production and is due to begin shooting in Abu Dhabi in the United Arab Emirates in mid-May (14), according to The Hollywood Reporter. Other scenes will be filmed at Pinewood Studios in the U.K.
Star Wars: Episode Vii is scheduled to hit movie theatres in December, 2015.