As fighting escalated on the ninth day of the U.S.-Israeli assault on Iran, the first U.S. pope warned that the conflict was fueling fear and hatred and raised concerns that it could spread further.

"Alongside the episodes of violence and devastation and the widespread climate of hatred and fear, there is also growing concern that the conflict could spread and that other countries in the region, including dear Lebanon, could once again sink into instability," Leo said at the Angelus prayer in St. Peter’s Square.

"Let us raise our humble prayer to the Lord that the roar of bombs may cease, that weapons may fall silent, and that space may be opened for dialog in which the voices of peoples can be heard," he added.

The Vatican's top diplomat warned on Wednesday that the U.S.-Israeli strikes undermined international law and said nations did not have a right to launch "preventive wars," an unusually direct criticism of the military campaign.