"You won't find a more devoted supporter of the 'Bourne' franchise than me," the director began in a statement issued to AccessHollywood.com.
"I will always be grateful to have been the caretaker to Jason Bourne over the course of 'The Bourne Supremacy' and 'The Bourne Ultimatum.' I'm very proud of those films and feel they express everything I most passionately believe about the possibility of making quality movies in the mainstream. My decision to not return a third time as director is simply about feeling the call for a different challenge. There's been no disagreement with Universal Pictures. The opportunity to work with the 'Bourne' family again is a difficult thing to pass up, but we have discussed this together and they have been incredibly understanding and supportive. I've been lucky enough to have made four films for Universal, and our relationship continues. Jason Bourne existed before me and will continue, and I hope to remain involved in some capacity as the series moves on."
ThePlaylist.com, which was the first Blog site to report Greengrass' departure, cited a disagreement between the director and the studio over Greengrass not being consulted over the hiring of a new script writer.
TheWrap.com, which was the first mainstream media site to report the director's exit, claims that it was Universal's unwillingness to push the film back a year and a half to 2012, which lead to the director not moving forward.
Whether or not a fourth incarnation of the franchise moves forward is entirely speculative at this point, but the power does seem to rest in Damon's hands.
Greengrass and Damon most recently paired up with Universal for the upcoming "Green Zone," set for release in May 2010.
Related Content from AccessHollywood.com:
VIEW THE PHOTOS: Scenes From 'The Bourne Ultimatum'
PLAY IT NOW: Trailer: Matt Damon's 'Green Zone'
PLAY IT NOW: Matt Damon's 'The Informant!' Premiere, New York