Pope Francis has written a "heartfelt appeal" to Vladimir Putin, urging the Russian president to steer the G20 summit towards a peaceful resolution of the Syrian crisis.
The Pope's letter tells Putin, who is chairing the summit in his capacity as G20 president, that war in Syria would be a "futile pursuit" and a "deliberate negation of international harmony".
Francis writes: "To the leaders present [at G20], 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.
"Rather, let there be a renewed commitment to seek, with courage and determination, a peaceful solution through dialogue and negotiation of the parties, unanimously supported by the international community."
According to the Pope, "one-sided interests" have thwarted attempts to bring peace to Syria since the country's civil war began two years ago. Now, he says, "the leaders of the G20 cannot remain indifferent to the dramatic situation of the beloved Syrian people which has lasted far too long, and even risks bringing greater suffering to a region bitterly tested by strife and needful of peace."
The letter ends with one final call for diplomacy and dialogue. "All governments have the moral duty to do everything possible to ensure humanitarian assistance to those suffering because of the conflict, both within and beyond the country's borders."
Earlier, the Vatican categorically denied a report in Argentine newspaper Clarin that the Pope had called Assad, asking him to stop the repression of the rebels in the country and take a more conciliatory attitude towards the opposition.
Clarin is a respected newspaper and the article was authored by Sergio Rubin, an Argentine journalist who has written the only authorised biography of the Pope.
The paper speculated that Francis could call the White House to try and persuade Obama not to attack Syria.