Pope Leo on Sunday said the international community must strive to avoid war that risks opening an "irreparable abyss," and that diplomacy should take the place of conflict.

U.S. forces struck Iran's three main nuclear sites overnight, joining an Israeli assault in a major new escalation of conflict in the Middle East as Tehran vowed to defend itself.

"Every member of the international community has a moral responsibility: to stop the tragedy of war before it becomes an irreparable abyss," Pope Leo said during his weekly prayer with pilgrims.

"No armed victory can compensate for the pain of mothers, the fear of children, the stolen future. Let diplomacy silence the weapons, let nations chart their future with peace efforts, not with violence and bloody conflicts," he added.

"In this dramatic scenario, which includes Israel and Palestine, the daily suffering of the population, especially in Gaza and other territories, risks being forgotten, where the need for adequate humanitarian support is becoming increasingly urgent," Pope Leo said.