VATICAN CITY (AP) — Pope Benedict XVI said today he lacks the strength to fulfill his duties and on February 28 will become the first pontiff in 600 years to resign. The announcement sets the stage for a conclave in March to elect a new leader for world's 1 billion Catholics. The 85-year-old pope announced the bombshell in Latin during a meeting of Vatican cardinals, surprising even his closest collaborators, even though Benedict had made clear in the past he would step down if he became too old or infirm to do the job. Benedict called his choice "a decision of great importance for the life of the church." There are several papal contenders in the wings, but no obvious front-runner — the same situation when Benedict was elected pontiff in 2005 after the death of Pope John Paul II.