ROME — Pope Leo XIV has marveled at the “huge learning curve” he has taken on as pontiff and likened some aspects of the job to jumping “in on the deep end of the pool very quickly,” in excerpts of an interview released Sunday on his 70th birthday.

History’s first American pope said he had quickly found his footing as a pastor for the universal Catholic Church, but discovered the diplomatic job of being pope was more challenging.

“The totally new aspect to this job is being thrown onto the level of world leader,” he was quoted as saying. “I’m learning a lot and feeling very challenged, but not overwhelmed. On that one I had to jump in on the deep end of the pool very quickly.”

The interview was conducted by Vatican correspondent Elise Ann Allen for her forthcoming biography of Leo. Excerpts were published Sunday on Allen’s Catholic news site Crux, and in the El Comercio daily of Peru.

In the excerpts, Leo spoke about feeling both American and Peruvian, given his 20 years of missionary experience in Peru. He said that experience gave him great insight into and appreciation of the Latin American church and Pope Francis’ ministry as history’s first South American pope.

Asked whether he would root for the U.S. or Peru in a future World Cup, Leo drew parallels to his childhood in Chicago and the value of not shutting down opponents.

“Even at home, I grew up a White Sox fan, but my mother was a Cubs fan, so you couldn’t be one of those fans that shut out the other side,” he said. “We learned, even in sports, to have an open, dialogical, friendly and not angry competitive stance on things like that, because we might not have gotten dinner had we been!”

Francis promoted Leo to a top job at the Vatican in 2023, making clear he viewed him as a potential successor. Nevertheless Leo said he wasn’t fully prepared for the job and still had a ways to go.

“There’s still a huge learning curve ahead of me,” he said.

Leo’s 70th birthday is celebrated at the Vatican

The interview was released Sunday as Leo marked his 70th birthday, which was celebrated at the Vatican during his traditional noon blessing.

Leo saw giant “Happy birthday” banners, in English, Italian and Spanish, balloons and congratulatory signs held up by the faithful gathered in St. Peter’s Square. Groups of Peruvian believers, including dancers in traditional attire, were out in force.

“My dears, it seems you know today I have turned 70,” Leo said to cheers. “I thank the Lord, my parents and all those who remembered me in their prayers.”

Later Sunday, Leo was spending his birthday afternoon presiding over an ecumenical prayer service in honor of 21st-century martyrs.

When he was elected last May at age 69, the former Robert Prevost was the youngest pope since 1978, when Karol Wojtyla was elected Pope John Paul II at age 58.

Many people in the square knew it was Leo’s birthday and wished him well, especially given the weight of responsibility he had taken on to run the Catholic Church.

“Well, he definitely needs a lot of support, because he has to carry on a pontificate during a particularly difficult period, both for geopolitical issues and certainly for internal matters,” said Lorenzo Vecchio, a member of a Catholic university group in the piazza. “We are certainly happy that he is a very young pope.”

Italian Premier Giorgia Meloni, for her part, issued a special greeting thanking Leo for his preaching, which she said was a source of inspiration. Leo’s teachings, she said in a statement, “provide reliable and solid guidance in extremely complex times, when certainties seem to waver and changes are as sudden as they are profound.”

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Associated Press video journalist Paolo Santalucia in Vatican City contributed to this report.