Pope Francis has urged leaders of the Group of 20 nations to abandon the "futile pursuit" of a military solution in Syria and work instead for dialogue and negotiation to end the conflict.
In a letter to the G20 host, Russian president Vladimir Putin, Francis lamented that "one-sided interests" had prevailed in Syria, preventing a peaceful solution and allowing the continued "senseless massacre" of innocents.
Francis has escalated his call for peace in Syria amid threatened US-led military strikes following a chemical weapons attack.
The pontiff will host a peace vigil in St Peter's Square on Saturday.
On Thursday, the Vatican summoned ambassadors accredited to the Holy See to outline its position, calling for respect for all minorities, including Christians, and that Syria's opposition forces distance themselves from extremists.