Earlier this month, we brought you the news about 14-year old British actor Asa Butterfield (Hugo, Merlin) being sought for the titular role of Ender Wiggin in director Gavin Hood‘s adaptation of Orson Scott Card‘s Hugo and Nebula Award-winning sci-fi novel Ender’s Game.

Now, Variety reports that Butterfield is locked for the lead role and the studio has now turned their attention to casting the role of Colonel Hyrum Graff. Viggo Mortensen (Everyone Has a Plan) had reportedly been a favorite for the role and even entered talks, which fell apart. Producers are now looking at more veteran actors for the role, including Harrison Ford (Cowboys & Aliens).

About Ender’s Game:

Set in Earth’s future, the novel presents an imperiled humankind who have barely survived two conflicts with the Formics (an insectoid alien race also known as the “Buggers”). In preparation for an anticipated third invasion, an international fleet maintains a school to find and train future fleet commanders. The world’s most talented children, including the novel’s protagonist, Ender Wiggin, are taken at a very young age to a training center known as the Battle School. There, teachers train them in the arts of war through increasingly difficult games including ones undertaken in zero gravity in the Battle Room where Ender’s tactical genius is revealed.

Ender’s Game is slated to hit theaters on March 15th, 2013.