VATICAN CITY, JAN. 23, 2005 ( John Paul II appealed for "tireless" prayer for the unity of Christians, and encouraged young people to become witnesses of full communion.

"Pray for the full communion of Christians. The world expects your evangelical testimony of unity!" the Holy Father said.

The Pope made his appeal before today leading the crowds gathered in St. Peter's Square in praying the midday Angelus. The appeal came amid the Week of Prayer for Christian Unity.

"I invite the Christian communities to live intensely this annual spiritual event, in which we have a foretaste, in a certain sense, of the joy of full communion at least in desire and unanimous invocation," he said.

"One is ever more clearly aware that unity is, in the first place, a gift of God to be implored tirelessly in humility and truth," he added.

The Holy Father prayed to the Virgin Mary to help Christians "to overcome every obstacle and to obtain this gift as soon as possible."

"From my heart I exhort all believers, especially young people, to prolong the ecumenical commitment during the whole year and to become in every place instruments and witnesses of the full communion invoked by Christ in the cenacle," the Pope continued.

The Week of Prayer for Christian Unity will conclude in Rome with the celebration of vespers this Tuesday in the Basilica of St. Paul Outside the Walls.

"I will unite myself spiritually to that liturgy, in which representatives from other Christian Churches and confessions will participate, and which will be presided over by Cardinal Walter Kasper, president of the Pontifical Council for Promoting Christian Unity," John Paul II said.