Pope Francis on Sunday invited people of all faiths to join him and the world's Catholics in a day of prayer and fasting on Sept. 7 to end the conflict in Syria.
Addressing tens of thousands of people in St. Peter's Square, he issued a long, impassioned appeal for peace in Syria and across the Middle East, saying God and history would be the judge of those who promoted violence or prevented peace.
Francis condemned the use of chemical weapons, blamed by Western powers on Syrian government forces, but added: "War, never again".
The United States and France are considering military action against Damascus in response to the chemical attack but Francis urged the international community to make every effort to bring about peace based on "dialogue and negotiations".
"Violence never leads to peace, war leads to war, violence leads to violence," he said.
The pope asked the 1.2 billion Roman Catholics around the world to pray for peace in Syria and observe a day of prayer and fasting on Saturday.
Francis announced his initiative a day after a meeting of top Vatican officials on Syria. He said he would lead a special prayer service in St. Peter's Square on Saturday between 7 p.m. and midnight.
The pope invited other Christians, members of other religions and all "people of goodwill" to join the Catholic initiative in any way they saw fit.
The peace initiative is reminiscent of several made by the late Pope John Paul, including one in which he dispatched envoys to Iraq, the United States and European capitals in 2003 to try to avert war in Iraq.
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