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.

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.