The Pope made his plea Saturday in the Basilica of St. Paul Outside the Walls during solemn vespers that closed the Week of Prayer for Christian Unity.
"The theme of peace remains as urgent as ever," he said. "It makes particular demands on the followers of Christ, the Prince of Peace, and it represents a challenge and a commitment for the ecumenical movement."
At the vespers, which were ecumenical in character, the Pope recognized that the goal of full unity among Christians experiences "the difficulties, the problems, and at times the disappointments which we still encounter."
"But the Holy Spirit never ceases to surprise us and he continues to work extraordinary wonders," he added. "This is why we need to stress the importance of spiritual ecumenism, which constitutes the soul of the whole ecumenical movement."