The sequel to "Halo," the most successful game yet for Microsoft Corp.'s Xbox game console, will not come out this year despite speculation to the contrary, the game's developer said on its Web site. Developers Bungie Studios said "Halo 2" would not be released this year, due to the time constraints of producing the game while also doing versions of the original "Halo" for the PC and Macintosh, according to a note posted Friday on the site. "We're still not ready to pick a specific release date, but we do want to state for the record that Halo 2 will not ship in 2003," the note said. "This game is a vast undertaking, considerably more complex than any of our previous efforts, and there is just no way to squeeze all of the necessary work into this calendar year." The original "Halo" came out with the launch of the Xbox in November 2001, and the military action game, featuring the "Master Chief," quickly became the console's marquee title. When Microsoft announced a sequel last year, most in the industry assumed it would be out in time for the 2003 holiday season. Bungie did say it would show some of "Halo 2" at E3, the video game industry's main trade show, this May in Los Angeles.