NEW YORK – A theologian recalls the then-cardinal’s deep understanding of Protestantism. A former U.S. ambassador to the Vatican was impressed by his interest in all things American.

Those who have met Pope Benedict XVI say the nation should expect a man who knows and admires much about the U.S., but also sees a culture in need of moral guidance.

Benedict arrives late Tuesday for a six-day visit to Washington and New York filled with high-profile events. He will meet President Bush at the White House, address leaders in Roman Catholic higher education, speak at the U.N., visit ground zero and hold two stadium Masses before leaving Sunday night.

It will be the first papal visit by Benedict since he was elected in 2005. However, the former Cardinal Joseph Ratzinger – who will celebrate a birthday and the anniversary of his election to the papacy while in the U.S. – traveled to America five times during his many years as the Vatican’s doctrinal watchdog.

The Rev. David Wells, a theologian at Gordon-Conwell Theological Seminary, a prominent evangelical school outside Boston, met Ratzinger years ago at a conference.

During a coffee break, the Roman Catholic cardinal picked up on a point Wells had made, launching into a detailed discussion of the “Institutes of the Christian Religion,” the seminal theological book by John Calvin and a key work on the Reformation.

“I was very impressed by the wide range of his knowledge, his lucidity and the grasp of the issues, both historical and contemporary,” Wells said.

Benedict, a former theology professor, has made ecumenical outreach a cornerstone of his papacy, although he has upset some Protestants by affirming that the Catholic Church is the only “true” church. The pope is holding a prayer service with Protestant and Orthodox Christian leaders Friday night at a Manhattan parish.

Ray Flynn, the former Boston mayor who served as U.S. ambassador to the Vatican from 1993 to 1997, recalled Ratzinger walking by a newsstand outside St. Peter’s Square where Flynn was looking at papers. Ratzinger stopped and discussed American current events with Flynn for nearly 20 minutes.

“I was just amazed by his level of curiosity and awareness about all that was taking place in the U.S.,” Flynn said. “He kept using the phrase, ‘the generosity of the United States.'”

Flynn is among those hosting a birthday party for Benedict on Wednesday night, his 81st birthday, in Washington. It’s not clear whether the pope will attend. The party is among several events related to the visit that aren’t on Benedict’s official itinerary. He is expected to meet privately with religious representatives and other leaders.

Some Catholics have expressed disappointment that the pope isn’t visiting the Archdiocese of Boston. The clergy sex abuse crisis erupted there in 2002 with the case of one predator priest, then spread nationwide and beyond. Abuse-related costs, including massive settlements with victims, have surpassed $2 billion for American dioceses since 1950.