The movies, based on J.R.R. Tolkien's books, had been delayed by union issues and the ongoing restructuring of flailing Hollywood studio Metro-Goldwyn-Mayer Inc., which owns half the project.
Jackson also co-wrote the screenplays with del Toro and three others.
Warner Bros. said the two-part prequel to the "Rings" trilogy is expected to start shooting in February.
The two movies will be shot back to back using digital 3-D cameras.
The Associated Press contributed to this report.
