VATICAN CITY, DEC. 14, 2003 ( God's love is the foundation of Christian joy, which no trial or suffering can affect, John Paul II said as he invited Christians to prepare spiritually for Christmas.

"Advent is a time of joy, because it makes us relive the expectation of the happiest event in history: the birth of the Son of God of the Virgin Mary," the Pope said today before praying the midday Angelus.

On the Third Sunday of Advent, the Pope dedicated his reflection -- addressed to several thousand pilgrims gathered in St. Peter's Square -- to Christian joy.

"To know that God is not far but close, not indifferent but compassionate, not a stranger but a merciful Father who follows us lovingly while respecting our freedom -- all this is reason for profound joy that different daily events cannot affect," he said.

"An unmistakable characteristic of Christian joy is that it can coexist with suffering, because it is totally based on love," added the Pope, who read his address in a clear voice.

"In fact, the Lord who is at hand, to the point of becoming man, comes to infuse in us his joy, the joy of loving," he said.

"Only in this way can one understand the serene joy of the martyrs even in the midst of trials, or the smile of charity of the saints before those who are suffering: a smile that does not offend but consoles," the Pope concluded.