"Six years ago we held off" commenting negatively about the administration after the terrorist attacks on the United States, Redford said in opening the festival, Fox News reported Friday.
"But considering what's happened, I think we're owed an apology," Redford told the audience.
The festival opened Thursday with Brett Morgen's "Chicago 10," a film that centers on the anti-Vietnam War demonstrations of the Chicago 1968 Democratic National Convention in which protesters clashed with police and soldiers.
The Sundance Film Festival, which runs through Jan. 28, features new work from American and international independent filmmakers. It is part of the Sundance Institute, founded by Redford, an award-winning actor and director.