The executive committee of the WCC said in a statement that it "strongly deplores the fact that the most powerful nations of this world again regard war as an acceptable instrument of foreign policy".
"War against Iraq would be immoral, unwise, and in breach of the principles of the United Nations Charter," it added after a meeting.
Warning of a humanitarian crisis of "grave magnitude", the WCC also appealed to the UN Security Council to "strictly limit the legitimate use of military force and to refrain from creating negative precedents and lowering the threshold for using violent means to solve international conflicts".
The statement also lauded "the courageous stance" of church leaders, especially in the United States and the United Kingdom, "in direct opposition to the positions taken by their political leadership." On Thursday, the leaders of Britain's two major Christian churches joined growing public opposition to military action, voicing doubt about Blair's moral argument and urging more time for UN weapons inspections.
"20 years of inspections are more effective, less costly and more relevant than 20 days of war," the WCC executive committee said at the beginning of its meeting on Monday.
The WCC also expressed concern about Iraqi human rights violations.
It recognised the need to disarm Iraq, but it also said there was a need "to make the whole Middle East region free from weapons of mass destruction".
The WCC groups 342 Christian churches -- Protestant, Anglican and Orthodox, but not the Roman Catholic Church - Sapa-AFP.