According to the United States Flag Code, the Pledge of Allegiance currently reads:
I pledge allegiance to the Flag of the United States of America, and to the Republic for which it stands, one Nation under God, indivisible, with liberty and justice for all.
Regardless of creed or following, there is no room in our government for any religious interference or reference. While many would argue that the United States is "a Christian nation", there must also be separation of Church and State at all levels. If individuals wish to add "under God" on their own they may, but "under God" should be removed from the official text of the Pleadge that represents our nation.
History: http://en.wikipedia.org/wiki/Pledge_of_Allegiance#Controversy