SEGA has confirmed that while the PlayStation 2 and PC versions of the game will be able to interact, the Xbox 360 version will not.
Following earlier reports on the Phantasy Star fan-site PSO World, SEGA has confirmed to EuroGamer that players of the Xbox 360 version of Phantasy Star Universe will be restricted to playing with other Xbox 360 gamers. Meanwhile PC and PlayStation 2 players will be able to mingle in the online world.
The reasons behind the decision haven't been disclosed, but given Xbox Live's multi-million subscriber base it shouldn't be too difficult to find people to play with. Phantasy Star Universe is scheduled for release on Xbox 360, PlayStation 2 and PC in the autumn.