Catholic faithful have gathered at the Vatican's St Peter's Square to celebrate Pope Leo's 70th birthday. Italy's Prime Minister Giorgia Meloni also paid tribute to the US-born pontiff.Pope Leo XIV on Sunday greeted the well-wishers who came to Vaticanto mark his 70th birthday. "My dears, it seems you know today I have turned 70," said Leo, the first American to lead the Catholic Church, after the traditional Sunday Angelus prayer. "I thank the Lord, my parents and all those who remembered me in their prayers," he added. Italian Prime Minister Giorgia Meloni sent birthday wishes to the Pope, saying that his teachings are "a solid guide in extremely complex times." Chicago-born Leo, whose given name is Robert Prevost, spent his birthday afternoon presiding over an ecumenical prayer service in honor of 21st-century martyrs. When he was chosen last May as the successor to late Pope Francis, Leo was the youngest pope since 1978, when Karol Wojtyla was elected Pope John Paul II at the age of 58. Leo admits 'huge learning curve' for his papacy In excerpts of an interview released Sunday on his 70th birthday, Pope Leo said there is "still a huge learning curve" ahead of him. Leo, who spent two decades in Peru, stated that "the totally new aspect to this job is being thrown onto the level of world leader." He added that he had "had to jump in on the deep end of the pool very quickly." Vatican correspondent Elise Ann Allen interviewed Leo for her forthcoming biography of the pope, which is set to be published in Spanish on September 18. Excerpts were published on Allen's Catholic news site Crux. Edited by: Darko Janjevic