VATICAN CITY, FEB. 17, 2002 ( The devil is more effective when he goes undetected, John Paul II reminded the faithful today as he pointed out the weapons a Christian has for combating temptations.

"Every man, in addition to his own concupiscence and the evil example of others, is also tempted by the devil, especially when least aware of it," the Holy Father said from the window of his study before praying the midday Angelus.

Addressing the thousands of pilgrims who had gathered in St. Peter´s Square below, the Pope said: "How many times [man] easily gives in to the false enticements of the flesh and the evil one, and then experiences bitter disappointments."

On this First Sunday of Lent, when Mass-goers heard the Gospel passage on the temptations of Jesus, the Pope called for vigilance "to react promptly to every onslaught of temptation."

The Holy Father pointed out the weapons a Christian has "for the daily combat against evil suggestions": "prayer, the sacraments, penance, careful attention to the Word of God, vigilance and fasting."

These ascetic means, inspired by the very example of Christ, are still indispensable because "the devil, ruler of this world, continues his deceitful action even today," the Holy Father said.

The Pope encouraged Christians "to undertake the penitential Lenten journey with greater determination, to be prompt in defeating every seduction of Satan and arrive at Easter in the joy of the spirit."

Before bidding the faithful farewell, John Paul II asked the Catholics of the world to pray for him and his collaborators, who this week are doing their annual retreat, the Spiritual Exercises.

The prayer of the faithful can help to make these days "fruitful," not "only for those who participate, but for the whole Church," the Pontiff said.

John Paul II began the retreat at 6 p.m. The preacher is Franciscan Cardinal Claudio Hummes, archbishop of Sao Paulo, Brazil. The theme of the retreat is "Always Christ´s Disciples." It ends Saturday morning.