Description:Pope Benedict greets thousands gathered for New Year's mass in St Peter's Basilica in the Vatican. The 84-year-old pontiff, who is believed to be suffering from arthritis, is wheeled up the central aisle on a mobile platform. The Vatican says it is to conserve his strength, allow more people to see him and guard against potential attacks. On the day the Roman Catholic Church marks its annual World Day of Peace, the pope's message to the crowds gathered in St Peter's Square.(1:28)