The widely expected announcement -- which had been rumored for several weeks -- came Thursday afternoon jointly from exec producers Peter Jackson and Fran Walsh, New Line president Toby Emmerich, and Mary Parent, newly named chief of MGM’s Worldwide Motion Picture Group.

Del Toro’s moving to New Zealand for the next four years to work with Jackson and his Wingnut and Weta production teams. He’ll direct the two films back to back, with the sequel dealing with the 60-year period between “The Hobbit” and “The Fellowship of the Ring,” the first of the “Lord of the Rings” trilogy.

New Line is overseeing development and will manage production. Both pics are being co-produced and co-financed by New Line Cinema and MGM, with Warner Bros. distributing domestically and MGM handling international.

Del Toro won’t leave for New Zealand immediately as he’s still in post-production on U’s “Hellboy 2,” due out in July. His previous pic, “Pan’s Labyrinth,” was released through New Line’s Picturehouse and set a record as the highest grossing Spanish language film in U.S. box office history.

The official signing of Del Toro comes four months after New Line settled a lawsuit with Jackson over “The Lord of the Rings” and announced that it had agreed with MGM to turn J.R.R. Tolkien’s “Hobbit” into two live-action films. Sam Raimi had been preceived as the initial front-runner as director but Del Toro had emerged in recent months as the likely candidate.

The studios didn’t give a start date on production and don’t yet have a script. Though no screenplay deal’s been set, it’s expected that the “LOTR” scripting team of Jackson, Walsh and Philippa Boyens will collaborate with Del Toro.

With Del Toro blocking out four years for the project, it’s likely that the studios are aiming at starting shooting next year and releasing the films in late 2011 and 2012.

Jackson’s WETA stages, post-production and visual effects facilities -- built for “The Lord of the Rings” -- will be used for both films. And New Zealand will again be the site of Middle-earth, with the story centering on Bilbo Baggins taking the Ring of Power from Gollum.