Hundreds of thousands of people are expected to pack St. Peter's Square for the celebration, which formally installs Francis as the new leader of the world's 1.2 billion Roman Catholics.

　　Among the high-level guests, the spiritual leader of the world's Orthodox Christians, Bartholomew, is expected to attend.  He would be the first patriarch from the Istanbul-based church to witness a papal inauguration since the two branches of Christianity split nearly 1,000 years ago.

　　More than 30 delegations of other Christian churches, as well as representatives from the Jewish, Muslim and various other faiths, also will attend.

　　Argentine President Cristina Fernandez de Kirchner arrived prior to Tuesday, in order to meet with the new pope, who hails from her country.  U.S. Vice President Joe Biden, a Catholic, also is one of the political leaders in attendance.

　　The Vatican released Pope Francis' new coat of arms, which is similar to the one he used as Archbishop of Buenos Aires.  It features symbols of Jesus, his mother Mary and her husband Joseph, as well as the new papal trappings of a bishop miter and the crossed keys of the Holy See.

　　Vatican officials also released details of Francis' official ring, which once was offered to Pope Paul VI, who presided over the second half of the Second Vatican Council, which is credited with modernizing the Roman Catholic Church.

　　Francis will receive the ring during Tuesday's installation Mass.