Hollywood actor Ben Affleck was surprised to be offered the role of Batman because he was convinced he was too old to play the superhero.

The 42-year-old Argo star was caught off-guard when producers offered him the role in upcoming blockbuster Batman v Superman: Dawn of Justice and admits he was worried his age would be a problem.

He tells Entertainment Weekly, "My first reaction was, 'Are you sure?' At the time I was 40, 41, and had just finished Argo, and I felt like, 'This seems like a strange way to get to Batman.'"

However, Affleck later understood director Zack Snyder's vision when he realized Batman's alter-ego Bruce Wayne would be portrayed as an "ageing playboy".

Affleck adds, "He (the character) really keeps up the image of the playboy, actively... So you have more of a dichotomy which I thought was really fun, and a little sad, like the ageing playboy."

Batman v Superman: Dawn of Justice, also starring Henry Cavill, Amy Adams, Jeremy Irons and Jesse Eisenberg, is set for release in March, 2016.