LOS ANGELES • James Cameron is back to direct Terminator 6.

So is Arnold Schwarzenegger in the acting department, but he is not reprising his iconic role as the grim-humoured Terminator in the 1984 debut movie.

Cameron told The Arnold Fans website that the 70-year-old will most likely be cast as the human being who was the inspiration for the Terminator.

"Yeah, you got to ask yourself, 'Why did they make these characters look and sound like Arnold?' There has to be a reason," noted Cameron, who directed the first two movies in the franchise.

He is now planning a trilogy.

"There has to be a reason. So, yeah, it has flashed through my mind that there has to have been a prototype.

"There has to have been a guy whose DNA was harvested from - that they grew the organic outer layer that they grew the Terminator from... and that presumably was a real person at some point.

"I've asked myself these questions, but it's never been resolved."

Schwarzenegger has told entertainment portal The Playlist that he will report for work in March next year.