Pope Francis recently urged the Group of 20 leaders to abandon the "futile pursuit" of a military solution in Syria as the Vatican laid out its case for a negotiated settlement that guarantees rights for all minorities, including Christians.

In a letter to the G-20 host, Russian President Vladimir Putin, Francis expressed grief that "one-sided interests" had prevailed in Syria, preventing a diplomatic end to the conflict and allowing the continued "senseless massacre" of innocents.

"To the leaders present, to each and every one, I make a heartfelt appeal for them to help find ways to overcome the conflicting positions and to lay aside the futile pursuit of a military solution," Francis wrote as the G-20 meeting got under way in St. Petersburg.

Francis increased his call for peace in Syria amid a threatened military strike by the U.S. prompted by an August 21st chemical weapons attack near Damascus.

He will host a peace vigil in St. Peter's Square on Saturday, a test of whether his immense popular appeal will translate into popular support for his peace message.

The Vatican summoned ambassadors accredited to the Holy See to outline its position on Syria, with Archbishop Dominique Mamberti, the Vatican's foreign minister, noting that the sarin gas attack had generated "horror and concern" from around the world.

"Confronted with similar acts one cannot remain silent, and the Holy See hopes that the competent institutions make clear what happened and that those responsible face justice," Mamberti told the 71 ambassadors