BOB ABERNETHY, anchor: Pope John Paul II wrapped up his pilgrimage to Slovakia this past week, but his obvious physical frailty throughout the trip has set off a new round of questions about the state of his health and the future of his papacy. Kim Lawton has our report.

KIM LAWTON: On his four-day visit to Slovakia, the 83-year-old Pope looked exhausted most of the time. Parkinson's disease has curtailed his mobility. His breath was labored; his speech slurred. Aides had to complete his homilies for him. Despite the Pope's obvious difficulties, Vatican officials brushed aside suggestions that this may have been his last trip.

Those close to John Paul say he remains mentally sharp. But his clearly declining physical condition raises questions about how the Church would handle a papal health emergency. There are no Church rules for what to do if a pope becomes incapacitated.

Joining me with more on this is Father Tom Reese, editor of the weekly Catholic magazine AMERICA and author of several books, including INSIDE THE VATICAN.

Father Reese, I don't mean to imply that the Pope is on the brink of being incapacitated, but what would the Church do if there were a sudden, serious health crisis?

Reverend THOMAS J. REESE, S.J. (Editor-in Chief, AMERICA magazine): This is a very serious problem that the Church has to face and has not taken care of yet. In the United States, if the president becomes incapacitated, we have the 25th Amendment to the Constitution that tells us what to do. In the Catholic Church, we have no equivalent 25th Amendment to the Constitution. We had a Canon lawyer examine this issue for us in AMERICA magazine and we have the article on our Web page at americamagazine.org. And it's clear that there are no procedures for dealing with a pope who suddenly becomes incapacitated, if he cannot communicate -- if he cannot even resign. If he can resign, that can take care of the problem. But if he can't communicate, if he has a stroke, if he can't respond to questions, then we have a real constitutional crisis in the Catholic Church.