Divided Christians can and must be united in meeting the modern challenges of secularization, threats to human life, environmental destruction, war and injustice, Pope Benedict XVI said.

"It is precisely the desire to proclaim Christ to others and bring the world his message of reconciliation that makes one experience the contradiction of Christian divisions," the pope said Jan. 25 as he closed the Week of Prayer for Christian Unity.

Leaders of Orthodox, Anglican and Protestant communities in Rome joined the pope for the annual prayer service at the Basilica of St. Paul Outside the Walls, offering prayers and proclaiming the readings.

The Week of Prayer 2010 focused on the common Christian vocation to witness to Christ in the world.

When the modern ecumenical movement was launched, the pope said, it started with a conference of missionaries from different denominations who gathered in Edinburgh, Scotland, in 1910 to reflect on ways to promote Christian unity in order to preach the Gospel more effectively.

The obvious question, he said, was: "How, in fact, can unbelievers accept the proclamation of the Gospel if Christians, while all referring to the same Christ, are in disagreement among themselves?"

Unity is "a particularly important condition for greater credibility and effectiveness," the pope said.

Unfortunately, Christians still are divided on important issues of dogma, doctrine and church discipline, which must be overcome through prayer and theological dialogue, he said.

At the same time, the pope said, Christians already can proclaim together "the fatherhood of God, Christ's victory over sin and death through his cross and resurrection (and) trust in the transforming action of the Spirit."

"While we are on the path toward full communion, we are called to offer a common witness in the face of the increasingly complex challenges of our time, such as secularization and indifference, relativism and hedonism, delicate ethical themes regarding the beginning and end of life, the limits of science and technology and dialogue with other religious traditions," he said.

The pope told the Christian leaders that they also must work more closely on "safeguarding creation, the promotion of the common good and peace, the defense of the centrality of the human person (and) the commitment to defeating the miseries of our time, such as hunger, poverty, illiteracy and the unequal distribution of goods."

Pope Benedict said working for Christian unity is not a specialty to which a few individuals or a few churches are called, but rather it is part of fulfilling Christ's will for all those who follow him.

Unity is something for which all Christians must work and pray, he said.

CNS