ROME (AP) — Pope Leo XIV on Saturday named a veteran Vatican diplomat as his new ambassador to the United States to manage one of the Holy See’s most important bilateral relationships at a crucial time, with ties strained over the Trump administration’s war in Iran and immigration crackdown.

Italian Archbishop Gabriele Caccia, 68, is currently the Holy See’s ambassador to the United Nations in New York. He replaces French-born Cardinal Christophe Pierre, who at age 80 is retiring as apostolic nuncio in Washington.

Caccia served as the Holy See’s ambassador to Lebanon and the Philippines before being posted to the U.N. in 2019. Ordained a priest in Milan in 1983, Caccia later served as “assessor” in the Vatican secretariat of state, a key administrative post in the Holy See's most important office.

He inherits a complicated and consequential dossier on both the U.S. church and state fronts at a time of global turmoil.

Pierre’s tenure as ambassador was notable for clear signs of friction between the leadership of the U.S. Conference of Catholic Bishops, which tends to skew conservative, and the more progressive priorities of Pope Francis’ pontificate.

The relationship with the U.S. and its church is crucial for the Holy See, not least because U.S. Catholics are the most generous donors to the Holy See’s coffers.

Leo, history’s first U.S.-born pope, is well aware of the dynamic, having served as Francis’ point man on bishop nominations for two years before his 2025 election. Leo has emphasized a message of pacification and unity in the church.

The first Trump administration clashed with Francis especially on migration, and that tension has continued in Leo’s pontificate and the second Trump term. Leo has repeatedly insisted that the Trump administration respect the human dignity of migrants, while acknowledging its right to its borders.

More recently, Leo has expressed “profound concern” about the U.S.-Israeli war in Iran and urged both sides to “stop the spiral of violence before it becomes an irreparable abyss.”

In comments last Sunday, Leo called for the resumption of diplomacy. Weapons, he said, only sow “destruction, pain and death.”

In a major foreign policy speech earlier this year, Leo also made clear he opposed the U.S. aggressive use of military power, in an apparent reference to Washington's incursion in Venezuela and threats to take Greenland. He denounced how nations were using force to assert their dominion worldwide and “completely undermine” peace and the post-World War II international legal order.

Caccia said in a statement Saturday he was humbled by Leo's appointment and faith in naming him ambassador to his native country.

“I receive this mission with both joy and a sense of trepidation,” according to a statement reported by Vatican News. He said his was a mission “at the service of communion and peace,” recalling that this year marks the 250th anniversary of the U.S. independence.

The current president of the U.S. conference, Archbishop Paul S. Coakley, welcomed Caccia’s appointment and offered the U.S. hierarchy’s “warmest welcome and our prayerful support.”

The Holy See has a tradition of diplomatic neutrality, though Leo has spoken out strongly against the humanitarian toll of Israel’s military action in Gaza and Russia’s invasion of Ukraine.