Christianity's largest ecumenical movement wants the U.S. and its allies to settle their dispute over Iran's nuclear program through negotiation because the Middle East should not suffer a another war.
The World Council of Churches - which brings together about 350 Protestant, Orthodox, and other churches representing more than 560 million Christians - also urged the complete withdrawal of U.S. forces from Iraq.
"Don't make war in Iran," the Geneva-based WCC said. The Roman Catholic Church is not a member of the council but cooperates with it.
U.S.-Iran tensions are running high over U.S. allegations that Iran is secretly trying to develop nuclear weapons and supplying Iraq's Shiite militias with weapons that have killed U.S. troops. Iran denies both claims.
The U.S. mission in Geneva declined to comment on the church group's statement. U.S. President George W. Bush said last month he was hopeful of convincing Tehran through peaceful means to give up any ambitions it has in developing a weapons program.
In a statement summarizing a meeting it held last week in Armenia, the World Council of Churches said the U.S. and its allies must "settle the dispute over Iran's nuclear program through negotiations and not through the use of military force."
"Threats to begin another war in the Middle East defy the lessons of both history and ethics," the statement said. "The region and its people must not suffer another war, let alone one that is unlawful, immoral and ill-conceived once again."
The church group also criticized Iranian belligerence toward the United States and Israel.
The World Council of Churches also called its members to pressure their governments "to break the international silence on the humanitarian crisis in Iraq" and provide more assistance to displaced and refugee Iraqis.
The organization said as a result of violence by non-state armed groups, regular armed forces and criminal groups, one Iraqi in six being internally displaced or fleeing outside the country.
The council expressed concern over the fate of Iraq's Christian communities, which represent only 4 percent of the country's population but make up what the group claimed was 40 percent of Iraq's refugees.
The statement praised "leading Muslim clerics who are using their authority to contain the violence in Iraq" and suggested that joint Christian-Muslim advocacy for tolerance and coexistence in Iraq would send "a powerful signal to Iraqis of all faiths."