Pope Leo took a veiled swipe at President Donald Trump Friday, saying that Christian political leaders who start wars should go to confession and assess if they are following the teachings of Jesus.

“Do those Christians who bear grave responsibility in armed conflicts have the humility and courage to make a serious examination of conscience and to go to confession?” the pope asked in a speech to priests.

While Leo did not name anyone, in recent days he has been ramping up calls for an end to the ongoing Iran war, which began with joint U.S.-Israeli airstrikes on Feb. 28.

U.S. President Donald Trump was raised in the Presbyterian Christian faith. Several of his top deputies, including Vice President JD Vance and Secretary of State Marco Rubio, are Catholic.

Jesus taught his followers to be non-violent. The Catholic Church generally opposes war.

For centuries, the Church has evaluated conflicts according to the just war tradition, which uses a series of criteria to evaluate whether a conflict can be considered morally justifiable, for example repelling an unjust invasion.

Washington, D.C. Cardinal Robert McElroy said earlier this week that the U.S.-Israeli strikes against Iran were “not morally legitimate” because they did not meet the Church’s just war criteria.

Leo was speaking Friday to a Vatican conference on the practice of confession, in which Catholics admit their sins to a priest and ask God’s forgiveness.

The pope said that the ritual helps individual Catholics and promotes peace and unity in society.

At least 2,000 people have been killed across the Middle East since the U.S. and Israel attacked Iran on February 28.

Gulf states hosting U.S. military bases and personnel, as well as Lebanon, were quickly drawn into the conflict.

Trump has given mixed signals about when the war could end. He said it was “pretty much complete” but then ramped up attacks on Iran again Friday.

Thirteen U.S. service members have been killed in the war so far, including six troops who died in a plane crash in Iraq Thursday.