Sumoward E. Harris, bishop of the Lutheran Church in Liberia, criticized a national campaign to make Liberia a "Christian nation."
It is the act of "a small radical group that does not stand for anything good or orderly," he said, vowing that the move wouldn't succeed.
Separation of church and state is written into Liberia's constitution.
Change proponents said they had collected more than the 10,000 signatures from citizens needed to propose a constitutional change.
Liberia is 85.5 percent Christian and 12.2 percent Muslim.
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