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