Ben Affleck has admitted some concerns about the caped crusader role.

"If I thought too hard about the actors who played this part before, I couldn't take the job," he told fans gathered at Comic-Con in San Diego.

But director Zack Snyder reassured the 42-year-old he was "perfect" casting.

"He's at the end of his rope. He's older; he's burned out... You're perfect for it" Snyder told the star.

Two-time Oscar winner Affleck follows in the footsteps of Michael Keaton, Val Kilmer, George Clooney and Christian Bale, as he steps into role of the masked vigilante - in a showdown with Henry Cavill's Superman.

Speaking at Comic-Con, where a new trailer for the film was shown, Affleck revealed an unexpected encounter with Bale - the previous incumbent of the Batman suit - in a store in LA.

"Before we started the movie I was getting my kid a Hallowe'en costume. My son is really into Batman," Affleck explained.

"We went to a costume store in Los Angeles... It was pretty empty. And I was in the aisle and I heard this 'Oi!', and I turned around, and it's Christian Bale!

"And there he and I were, standing in the Batman section."

"I said, 'Do you have any tips?'," Affleck recalled. "'And he said: 'Make sure you can piss in that suit.'"

Source: Press Release