The Argo actor admitted that he is behind schedule on finishing the screenplay for his adaptation of Dennis Lehane's Live By Night and felt it necessary to preserve as much time as possible to complete the script.
"Basically I'm doing this movie called Live By Night and I'm trying to meet this schedule... so that I can have it released at the right time," Affleck explained to MTV News.
"And basically I haven't gotten enough writing done; it became clear that if I took that job - it was in Buenos Aires for three months - I'd have to miss the deadline. I had to choose between getting the movie out when I wanted to or doing that movie."
He also expressed his disappointment at missing out on the opportunity to work with Focus star Kristen Stewart, adding: "Reluctantly I chose the latter but I love those guys, I love Kristen. I was really excited to work with her. I think the movie is going to be fabulous. I'm sure they'll find a great guy for it."
Affleck recently opened up about the career slump he experienced following his split from ex-girlfriend Jennifer Lopez in 2003.
Watch the trailer for Argo below: