NEW : Germany Secretary of St. Peter 's Basilica thanked Pope Benedict for his service . The pontiff will later celebrate an Africans Wednesday mass at State Tarcisio Bertone . Benedict cites age and frailty as the reasons for his surprise resignation . His successor as pope will be chosen at a conclave of cardinals in Wednesday .
NEW : Vatican Secretary of State Tarcisio Bertone thanked Pope Benedict for his service . The pontiff will later celebrate an Ash Wednesday mass at St. Peter 's Basilica . Benedict cites age and frailty as the reasons for his surprise resignation . His successor as pope will be chosen at a conclave of cardinals in March .