Pope Leo XIV will lead the Regina Coeli prayer from the balcony of St Peter's Basilica on Sunday, in his second official public appearance since becoming the leader of the Catholic Church.

The noon (1000 GMT) prayer is expected to draw thousands of people anxious for a closer look at the modest pontiff, born Robert Francis Prevost, who before becoming the first US pope spent much of his life as a missionary in Peru.

Cardinals chose Leo as the 267th pope at a secret conclave Thursday, praying he could heal rifts within the Church, renew faith among the world's 1.4 billion Catholics and address a host of modern-day challenges weighing on the more than 2,000-year-old institution.

Addressing cardinals on Saturday, the 69-year-old Leo called himself a "humble servant of God... and nothing more than this", and an "unworthy successor" to St Peter, according to a transcript of his speech released by the Vatican.

In the first clues as to the direction of his pontificate, he said he would be driven by the legacy of his predecessor, Pope Francis -- who died April 21 aged 88 -- "with his........

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