Pope Leo XIV denounced President Trump's threat to wipe out Iran's civilization on Tuesday.The big picture: The first U.S.-born pontiff told reporters in Italian "this threat against the entire people of Iran" is "truly unacceptable," according to a Vatican News translation.Leo has been increasingly outspoken in his moral opposition to many of Trump's policies, in particular on the Iran war and immigration, but his comments on Tuesday marked his most pointed rebuke yet.What they're saying: "There are certainly issues of international law here, but even more, it is a moral question concerning the good of the people as a whole, in its entirety," the pope told reporters in Italian.He's asking "all people of goodwill to search, always for peace and not violence. To reject war, especially a war which many people have said is an unjust war, which is continuing to escalate and which is not resolving anything," Leo told reporters as he switched to English.The pope noted the "worldwide economic crisis, energy crisis" and a situation in the Middle East of "great instability," which he said was "provoking more hatred throughout the world" as he called for negotiations to end the war."Attacks on civilian infrastructure is against international law ... it is also a sign of the hatred, the division, the destruction that the human being is capable of," Leo added.He urged "citizens of all the countries involved to contact the authorities, political leaders, congressmen, to ask them, tell them to work for peace and to reject war always."The other side: White House Press Secretary Karoline Leavitt, who is Catholic, said in response to the pope's criticisms last week that there's nothing wrong with Trump or military leaders "calling on the American people to pray for our service members."Representatives for the White House did not immediately respond to Axios' Tuesday afternoon request for comment.Go deeper: Trump's Iran threats raise moral stakes for military members