On the same day that Microsoft have released the first TV promo for Halo 2 (which you can download via the link below), it's become apparent that there will be no cooperative play via either system link-up or Xbox Live - even though it's been widely assumed that the game would include such a feature.
Instead, as per the co-op mode in the first game, two players will be able to make use of a split screen, although you now have the additional option of splitting it either horizontally or vertically. (Why not diagonally?)
Neither Microsoft or developers Bungie have revealed precisely why there's no online cooperative mode. However, in more promising Xbox Live news, Microsoft have confirmed that four players will be able to get involved with online Halo 2 via a four-way split-screen and a single Xbox Live account.
Halo 2 will be released for Xbox on 11 November