Microsoft previously announced the sci-fi action game grossed $170 million domestically on its first day, primarily from pre-orders.

"Halo 3" is believed to have sold 5 million units worldwide in its first week.

Only time will tell if the game will outsell the best-selling console video-game in recent times --"Grand Theft Auto: Vice City" -- which has moved more than 13 million units to date.

Microsoft also said the sale of its Xbox 360, the only console on which "Halo 3" can be played, has tripled compared with the previous weekly average.