VATICAN CITY (AP) — Pope Leo XIV, history’s first American pope, vowed Sunday to work for unity so that the Catholic Church becomes a sign of peace in the world, offering a message of communion during an inaugural Mass in St. Peter’s Square before an estimated 150,000 pilgrims, presidents, patriarchs and princes.

The pontiff said he would face up to "the questions, concerns and challenges of today’s world" and, in a nod to conservatives, he promised to preserve "the rich heritage of the Christian faith," repeatedly calling for unity.

The Vatican said some 200,000 people attended the Mass at St. Peter’s Square, which marked the start of the pontificate of the first American to lead the Roman Catholic Church. Vice President JD Vance was among the dignitaries.