TORONTO (Reuters) - Actor Christian Bale was in Toronto to promote his latest film "Hostiles" at the film festival, but it was his heavier frame and bleached eyebrows in preparation for his role as former U.S. Vice President Dick Cheney that grabbed the spotlight.

Bale, 43, said he swore he would not undergo another extreme physical transformation to play a character. But the lure of playing Cheney in "Backseat" and some arm twisting from filmmaker Adam McKay finally persuaded the actor to harness the transformation.

"I don't know why I'm doing that again. I kept on saying I can't do that again, but it's Adam McKay ... and the bastard went and wrote a really good script," Bale told Reuters at the premiere of "Hostiles" at the Toronto International Film Festival on Monday.

"I kept on trying to find reasons about how to say no and he always had an answer for me ... I eventually went, 'Damn it. He's right. I've got to do it, I've got to do it,'" he added.

Bale is known for physically transforming himself for his roles, losing more than 60 pounds and foregoing sleep to achieve a skeletal look for 2004's "The Machinist" before then bulking up to play Batman in Christopher Nolan's "Dark Knight" trilogy.

The actor told film trade publication Variety that he has "just been eating a lot of pies" to prepare for playing Cheney in "Backseat," which will follow the former vice president's influence and impact during his years in President George W. Bush's administration.

In director Scott Cooper's western period drama "Hostiles," Bales plays army captain Joseph J. Blocker, a reluctant escort for a dying Cheyenne war chief returning to his tribal lands.

(Reporting by Rollo Ross for Reuters Television and Solarina Ho; Editing by Piya Sinha-Roy and Dan Grebler)