Pope Benedict XVI (search) stepped up his appeals to Orthodox Christians on Wednesday, saying a unified church could help a world "full of skepticism and doubts" to believe.

Benedict acknowledged key differences but stressed areas of agreement during a Mass attended by a delegation from the spiritual leader of the world's 200 million Orthodox, Ecumenical Patriarch Bartholomew I (search).

Benedict has made improving relations with Christians, and healing the 1,000-year-old rift with the Orthodox, a "fundamental" priority of his papacy.

After centuries of moving apart, the churches formally split in 1054 over several issues, including the primacy of the pope, devotional differences, and Latin demands for priestly celibacy, while the Greek-influenced tradition permitted married clergy. Relations remain tense over Orthodox charges of proselytism and rival property claims in places such as Russia and eastern Europe.

In his homily, Benedict stressed the unity and universality of the church, but acknowledged key differences over the clout of the pope. The Orthodox see equal distribution of power among their churches, although Bartholomew is considered "first among equals."

"In this time of the world full of skepticism and doubts, but also rich in the desire for God, let us recognize anew our mission to witness Christ the Lord together, and on the base of that unity that he has given us, to help the world believe," he said.

During the Mass, Benedict bestowed the pallium, or a woolen shawl, on 32 metropolitan archbishops from around the world to symbolize their bond with the Vatican.

One of them was Archbishop Stanislaw Dziwisz, Pope John Paul II's (search) longtime private secretary who earlier this month was named archbishop of Krakow, Poland. Applause rang out when he went up to receive the pallium from the pope.

The Mass celebrated the feast of St. Peter and St. Paul. At the end of the service, Benedict and the leader of the Orthodox delegation, Metropolitan John of Pergamon, prayed together underneath St. Peter's Basilica at the tomb the faithful believe houses the remains of the apostle Peter.