Washington DC - Cardinal Robert McElroy, the archbishop of Washington, has said the US war on Iran is "not morally legitimate," adopting a stronger tone than that of Pope Leo XIV.

In an interview with the Catholic Standard, the magazine of the Diocese of Washington, the cardinal said the war did not meet the criterion for a "morally legitimate war" under Catholic teaching because US had not responded to an "existing or imminent and objectively verifiable attack by Iran".

"As Pope Benedict declared categorically, Catholic teaching does not support preventative war, i.e. a war justified by speculation about events in the future," he said in the interview published online Monday.

Nor should the war drag on, he said, "lurching from goal to goal and from strategy to strategy" given the US government's aims in attacking Iran have been "absolutely unclear."

"There is a logic to war that presses onward, escalating in its dimensions and timeline. Our country has fallen victim to this logic of war in the recent past, especially in the Middle East," he said, warning of an "ongoing morass in Iran."

"Lebanon may fall into civil war. The world's oil supply is under great strain. The potential disintegration of Iran could well produce new and dangerous realities. And the possibility of immense casualties on all sides is immense," he added.

At the weekend, another senior American cardinal, Blase Cupich, described a White House video montage that mixed Hollywood film clips with real footage of strikes on Iran as "horrifying" and "sickening."

The statements by the cardinals contrast with Leo XIV, who has not directly condemned the unprovoked strikes carried out by the US and Israel against Iran.

The Holy See traditionally maintains diplomatic neutrality. But its top diplomat, Italian Cardinal Pietro Parolin who serves as secretary of state, last week warned against the "erosion of international law" and the concept of a "preventative war" on Iran.