Surrounded by the same cardinals who elected him the day before, Pope Benedict XVI (search) held the first Mass of his papacy in the frescoed Sistine Chapel on Wednesday.

Benedict, the former Cardinal Joseph Ratzinger (search), clutched his pastoral staff and made the sign of the cross as he entered the intimate chapel, led by the cardinals.

Wearing golden vestments and a white bishop's miter, Benedict, the 265th Bishop of Rome (search), opened the Mass with a prayer in Latin and was to deliver his first homily in Latin — a discourse that will be watched by millions for hints about priorities in his pontificate.

Cardinals — also clad in gold — solemnly chanted the "Kyrie Eleison" hymn, Greek for "Lord have mercy."

In a message read in Latin at the end of the service, the pontiff pledged to continue the liberalizing reforms of the Second Vatican Council (search) and to work to unify all Christians, as he outlined goals following an election that sent a signal the church was intent on sticking to tradition as it confronts 21st-century problems.

He said his "primary task" would be to work without fail to reunify all Christians and that sentiment alone was not enough.

"Concrete acts that enter souls and move consciences are needed," he said.

The message was clearly designed to show that Benedict was intent on following many of the groundbreaking paths charted by John Paul II (search), who had made reaching out to other religions and trying to heal the 1,000-year-old schism between Eastern and Western Christianity a hallmark of his pontificate.

Joy over the selection of a new pope was mixed with worries that Benedict could polarize a global church, whose challenges include growing secularism in rich countries and inroads by evangelical groups in regions such as Latin America.

The new pope said he wanted to continue "an open and sincere dialogue" with other religions and would do everything in his power to improve the ecumenical cause.

Benedict referred to his predecessor several times in his message, including a reference to the late pope's final will, where John Paul said he hoped new generations would draw on the work of the Second Vatican Council, the 1962-65 meeting that modernized the church.

"I too ... want to affirm with decisive willingness to follow in the commitment of carrying out the Second Vatican Council, in the wake of my predecessors and in faithful continuity with the 2,000-year-old tradition of the church," he said.

John Paul, with then-Cardinal Ratzinger as his doctrinal enforcer, supported council reforms but cracked down on what both men considered excesses spawned by the changes, including calls for priests to be allowed to marry and admission of women into the priesthood.

The Vatican's hard-line enforcer of church orthodoxy under John Paul II for almost 25 years, Benedict had gone into the two-day conclave as one of the favorites to be elected pope. He emerged Tuesday as the oldest pontiff at the time of his election in 275 years and the first German pope in almost a millennium.

A wildly cheering crowd of more than 100,000 welcomed Benedict when he stepped onto the balcony of St. Peter's Basilica as dusk fell Tuesday and gave his first blessing as pope.

Pilgrims on St. Peter's Square shouted "Benedetto!", the Italian form of Benedict, and "Viva il Papa," waved national flags, hugged their neighbors and jumped in joy. Many shed tears of bliss; some wept in disappointment.

By contrast, St. Peter's Square was nearly empty early Wednesday, although by the end of the Mass a few hundred people had gathered to watch the proceedings on giant television screens.

"We greet our Pope Benedict XVI," read a poster toted by teens from a high school in Handrup, Germany, who were in the square when his black Mercedes convertible, its top up and Vatican flags flying, zipped into and out of his former offices at the Congregation for the Doctrine of the Faith (search), the successor body to the medieval Inquisition.

Ratzinger selected a name rich in European tradition — the first Pope Benedict, who ruled from 575-579, was declared the patron saint of Europe because of his involvement in forming Christian Europe. Vatican watchers said Ratzinger's selection of the name indicated he would emphasize the need to consolidate Europe's Christian roots.

Amid the joy, there also was disappointment Wednesday from some who viewed him as an obstacle to necessary change in the church.

"This election creates as much hope as fear," said Belgium's Deputy Prime Minister Laurette Onkelinx, who is responsible for government relations with religious communities.

"The fear is because of the past of the new pope — great defender of religious doctrine and a great conservative. One can fear he will not respond to the need for openness of the church," she said in an interview with Le Soir newspaper, insisting she was speaking in a personal capacity.

But American cardinals said Benedict had been unfairly caricatured as an unfeeling conservative, describing him instead as a caring, brilliant churchman who listens to those with opposing views.

"I think he'll play well as soon as people come to know him," said New York Cardinal Edward Egan (search). "This is a very unprepossessing, humble, and if I may say, lovely gentleman."

The pope's participation in the Nazi Party as a youth rang alarms in Israel.

"White smoke, black past," said the headline in the mass-circulation Yediot Ahronot. "From the Nazi youth movement to the Vatican."

The young Ratzinger, like all other teens, was enrolled in the Hitler Youth (search), and was later drafted into the army.

"He was 18 years old when the war ended so everything that he had to do with the Nazi regime was as a very young man," said Moshe Zimmerman, a professor of German history at the Hebrew University in Jerusalem (search). "I don't believe that there is any room for doubt that [the pope] of today is very different than the days he belonged in the Hitler Youth."

Jewish leaders said they were encouraged by his special interest in coexistence.

"I hope that the new pope will continue the same way and he will continue to build the same bridge as the last pope built in the past between the two nations, between the Christians and the Jewish nation," said Israel's chief rabbi, Yona Metzger.

But the Greek Metropolitan Bishop, Chrisostomos of Zakynthos, expressed concern Wednesday that Benedict may not work to unite Christians.

Unless his record changes, he said, "it will be a huge thorn, a great difficulty in continuing the efforts of his predecessors with the Orthodox for convergence, as was the will of Christ."

Benedict said he had been surprised by his election, and German Cardinal Joachim Meisner (search) told reporters late Tuesday that he had looked "a little forlorn" when he went to change into his papal vestments in the Room of Tears — a room that earned its nickname because many new pontiffs get choked up there, realizing the enormity of their mission.

Meisner added: "By the time dinner came around, Ratzinger was looking much better and very much like the pope."

Benedict asked cardinals to dine together on bean soup, cold cuts, a salad and fruit, Meisner said. The nuns who prepare their meals at the Vatican hotel where the cardinals were sequestered during the conclave didn't have time to plan a special menu, so there were only two special treats — ice cream and champagne.

In his first words as pope delivered from the loggia overlooking St. Peter's Square, Benedict paid tribute in accented Italian to "the great John Paul II." He called himself "a simple, humble worker in the vineyard of the Lord."

It was a sign of John Paul's charismatic legacy looming over the new pontiff, who is described by people who know him as intellectual, cultured and rather reserved.

Benedict said Wednesday he felt John Paul's presence as he wrestled with two conflicting emotions: thanks to God for the gift of being pope but also "a sense of inadequacy" in carrying out the responsibility.

"I seem to feel his strong hand holding mine. I feel I can see his smiling eyes and hear his words, at this moment particularly directed at me: 'Be not afraid.'"

Benedict turned 78 on Saturday, the oldest pope elected since Clement XII in 1730. His age clearly was a factor among cardinals who favored a "transitional" pope who could skillfully lead the church as it absorbs John Paul II's legacy, rather than a younger cardinal who could wind up with another long pontificate.

His election in four ballots over two days — the first of Tuesday's afternoon session — concluded one of the shortest conclaves in 100 years.

A conservative on issues such as homosexuality, the ordination of women and lifting the celibacy requirement for priests, Benedict has led the Vatican's Congregation for the Doctrine of the Faith — a position he used to discipline church dissidents and uphold church policy against attempts at reform by liberals and activist priests.

"God has taken the most unusual people and placed them in places of authority, power if you will, and used them for his purposes," said American Cardinal Adam Maida (search). "So I believe that Cardinal Ratzinger, with all his gifts and talents and even some of his shortcomings, will somehow be able to reach others."

British Cardinal Cormac Murphy-O'Connor (search) suggested Ratzinger might temper some of his positions, at least publicly, because of the office he now holds.

"The pope now has a platform and a place he didn't have before. Now he has much wider responsibilities, and I think he's aware of that," Murphy-O'Connor said, adding that Ratzinger was elected "notwithstanding his age."

"He could be a wedge rather than a unifier for the church," said the Rev. Thomas Reese, editor of the Jesuit weekly magazine America.

Among the crowd on St. Peter's Square, Benedict also brought out sharply differing reactions.

Evelyn Strauch, a 54-year-old housewife from Ratzinger's home state of Bavaria, buried her head in her hands and wept.

"This can't be true," she said. "I had hoped so much that we would get a good pope who would do something for women. ... This is so terrible."

Mark Wunsch, 27, a religious philosophy student from Denver, Colorado, was elated.

"The cardinals elected a good and holy man who was close to Pope John Paul II," he said. "He'll be a wonderful and good leader in preaching the truth and love."

Benedict inherits a range of pressing issues. These include priest sex-abuse scandals that have cost the church millions in settlements in the United States and elsewhere, chronic shortages of priests and nuns in the West, and calls for easing the ban on condoms to help fight the spread of AIDS.

And he has to follow in the footsteps of John Paul II, the global pontiff who made 104 international trips in his more than 26 years as pope and set new standards in reaching out to other religions.

In an indication that he would indeed travel and continue to reach out to young people like John Paul, Benedict said Wednesday he planned to attend the church's World Youth Day (search) celebrations in Cologne, Germany this August.

Two images of Ratzinger have emerged in recent days.

With his wispy silver hair blowing in the wind, the Bavarian prelate stood before the world's political and spiritual leaders at John Paul's funeral April 8 and offered an eloquent and sensitive farewell that moved some to tears.

Then, just before the cardinals entered the conclave Monday morning, he made clear where he stands ideologically, using words that John Paul would surely have endorsed.

He warned about tendencies that he considered dangers to the faith: sects and ideologies like Marxism, liberalism, atheism, agnosticism and relativism — the ideology that there are no absolute truths.

"We are moving toward a dictatorship of relativism which does not recognize anything as for certain and which has as its highest goal one's own ego and one's own desires," he said.

Benedict has denounced rock music, dismissed anyone who had tried to find "feminist" meanings in the Bible, and last year told American bishops it was appropriate to deny Communion to those who support abortion and euthanasia, a statement that became an issue in the American presidential campaign.

Ratzinger is the first German pope in nearly 1,000 years. His faith is rooted in Bavaria, the Alpine region with Germany's strongest Catholic identity. Like many of his generation, he carries the burden of Germany's past.

In his memoirs, the policeman's son wrote of being enrolled in the Hitler Youth against his will when he was 14 in 1941, when membership was compulsory. He says he was soon let out because of his studies for the priesthood.

In 1943, he was drafted into an anti-aircraft unit in Munich as a helper, a common fate for teenage boys too young to be soldiers. He wrote that he escaped recruitment in the dreaded Nazi SS, the party's private army, because he said he was a priest in training.

He and his older brother were ordained in 1951. He taught theology and earned a reputation as a forward-looking prelate. He took part in the 1962-65 Second Vatican Council, a major attempt to modernize the faith, but had some reservations.

Returning to Germany between sessions of the council, "I found the mood in the church and among theologians to be agitated," he wrote in his memoirs. "More and more there was the impression that nothing stood fast in the church, that everything was up for revision."

In 1977, Ratzinger was appointed bishop of Munich and elevated to cardinal three months later by Pope Paul VI. He was one of only two cardinals in the latest conclave who were not chosen by John Paul.