Pope John Paul is due to leave today on a gruelling 11-day tour of Canada, Guatemala and Mexico. The tour is likely to tax the ailing 82-year-old pontiff's strength to the limit.
The Pope has prepared for the 97th foreign journey of his pontificate by resting at his summer residence in the hills south of Rome and organisers have incorporated unprecedented rest periods into his usually hectic schedule. But the trip, which the Vatican had considered cancelling or curtailing after John Paul struggled to cope in Bulgaria and Azerbaijan last May, could be one of the Pope's last.
Some 15,000 miles, three time zones and more than 30 hours of flying would be tough going even for someone in the full bloom of health. For the Pope, who suffers from Parkinson's disease and arthritis, it will be yet another test of his remarkable endurance. To take account of his failing strength the Canada trip - to celebrate World Youth Day in Toronto - begins with three days of rest and recreation on an island in Lake Simcoe.
The Pope will be flown by helicopter to the church-owned retreat of Strawberry Island and will move around the grounds in a golf buggy.
The Pope's speeches will be kept to a minimum, but otherwise there are no particular health concerns, Mgr Renato Boccardo, the organiser of the trip, said.
The high point of the Canadian visit comes on Sunday, when the Pope is due to celebrate Mass for World Youth Day participants in Toronto's Downsview Park.
A large delegation is expected from the US and observers will be watching intently to see whether the Pope mentions the clerical sex abuse scandal.
The toughest part of the trip will come in the heat and poverty of Guatemala and Mexico. In Mexico City the Pope will proclaim a 16th century Indian peasant a saint. Juan Diego Cuauhtlatoatzin is widely revered for having seen the Virgin Mary in a vision.