He told the crowd in the square that thanks to Mary's openness to God's will, "the true light that illuminates every human being appeared and the path to peace was reopened."

"I invite all of you to join me in praying earnestly for peace throughout the world, for reconciliation and forgiveness in areas of conflict, and for a more just and equitable distribution of the world's resources," he said.

Earlier, during his homily at Mass, the pope said Jesus' birth changed human history, filling it with hope and promise.

"He is the mercy and the peace that the world, of itself, cannot give, and which it needs at least as much as bread," the pope said.

For World Peace Day 2012, Pope Benedict focused on the theme of educating young people in justice and peace.

"In the face of the shadows that obscure the horizons of today's world, to assume responsibility for educating young people in knowledge of the truth, in fundamental values and virtues, is to look to the future with hope," the pope said.

With the ease of communications, travel and globalization, he said, the world seems smaller in many ways and people come into contact more often with others from a different race, religion or culture.

"Now, more than ever, it is indispensable to learn the importance and the art of peaceful coexistence, mutual respect, dialogue and understanding," he said.

While young people naturally are open, the pope said they often are targets of manipulation by those who are intolerant and violent, so "a solid education of their consciences" is important.

Education begins in the family, which must help children "develop a personality that combines a profound sense of justice with respect for their neighbor, with a capacity to address conflicts without arrogance, with the inner strength to bear witness to good, even when it involves sacrifice, with forgiveness and reconciliation," Pope Benedict said.

Religious leaders must contribute to the process as well, he said, because "every pathway of authentic religious formation guides the person, from the most tender age, to know God, to love him and do his will."

At the evening prayer service New Year's Eve, the pope said most people look toward a new year "with some trepidation," with desires and expectations. But the changing of the civic calendar so soon after Christmas helps Christians recognize the purpose of their lives and look with confidence to the future.

"From within the fabric of humanity, rent asunder by so much injustice, wickedness and violence, there bursts forth in an unforeseen way the joyful and liberating novelty of Christ our savior, who leads us to contemplate the goodness and tenderness of God," the pope said.

"There is no more room for anxiety in the face of time that passes, never to return," he said. "Now there is room for unlimited trust in God, by whom we know we are loved, for whom we live and to whom our life is directed."