Cardinal Joseph Ratzinger (search) of Germany, the Vatican's chief overseer of doctrine, assumed the name Benedict XVI (search) Tuesday after he was elected pope of the Roman Catholic Church following one of the shortest conclaves in history.

Ratzinger — one of the closest friends and advisers to the late Pope John Paul II (search) — appeared on the balcony of St. Peter's Basilica to offer his first words and prayers as pontiff.

The cardinals "have elected me — a simple, humble worker in God's vineyard," he said in Italian to the excited crowd below.

"The Lord knows how to work and how to act … and I especially trust in your prayers,” he said.

The throngs responded by chanting "Benedict! Benedict!" to the church's 265th pontiff.

The first German pope since the 11th century then led a prayer and a blessing. Other cardinals, clad in crimson robes, came out on balconies to watch him.

The Vatican announced that Benedict XVI's Inaugural Mass will be Sunday at 10 a.m. in Rome (4 a.m. EDT).

The 115 red-robed men in the powerful College of Cardinals (search) of which Ratzinger was dean — were charged with electing the Roman Catholic Church leader and began their vote by secret ballot on Monday.

"This evening there was the election of the new pope, Cardinal Joseph Ratzinger, who took the name of Benedetto XVI," said Vatican spokesman Joaquin Navarro-Valls Tuesday. "At the end of the conclave, Benedetto XVI decided to have dinner with all the cardinals" and spend the night at the Vatican hotel, the Domus Sanctae Marthae.

The new pope will hold a 9 a.m. Wednesday Mass with the cardinals in the Sistine Chapel and deliver the homily in Latin, the Vatican said.

U.S. governmental leaders reacted with optimism to news of the new pope.

On the White House lawn, President Bush remembered the late Pope John Paul II with fondness and sent his prayers to Pope Benedict XVI, whom he called "a man of great wisdom and knowledge."

"He's a man who serves the Lord," Bush said Tuesday. "We remember well his sermon at the pope's funeral in Rome ... how his words touched our hearts and the hearts of millions. We join with our fellow citizens and millions around the world who pray for continued strength and wisdom."

Congressional leaders also expressed their support Tuesday.

"The incredible outpouring of love and appreciation for Pope John Paul II has been a profound testament to his life, to the power of faith and to the Catholic Church," House Democratic leader Nancy Pelosi said. "People around the world will now look to Pope Benedict XVI for inspiration and guidance.

"Cardinal Ratzinger earned the trust and respect of Pope John Paul II, who did God's work here on earth, seeking peace and justice for all. I hope that Pope Benedict XVI will build on that legacy."

Said Republican Senate Majority Leader Bill Frist: "Today ushers in a new era for the Catholic Church. I'm confident that Pope Benedict XVI is blessed with the same compassion and vision that made Pope John Paul II one of the world's most revered and respected voices.

"I join the world community in welcoming Pope Benedict XVI as leader of the Catholic Church and look forward to seeing how his good works continue spreading God's message of peace."

Ratzinger, who turned 78 on Saturday, served John Paul II since 1981 as head of the Congregation for the Doctrine of the Faith (search).

In that position, the man described as a conservative guardian of church doctrine disciplined church dissidents and upheld church policy against attempts by liberals for reforms.

The new pope had gone into the conclave with the most buzz among two dozen leading candidates. He had impressed many faithful with his stirring homily at the funeral of John Paul II, who died April 2 at age 84.

Not everyone was happy about his election to succeed John Paul II, however.

Jose Silvano, a 40-year-old travel agent from Brazil, called Ratzinger "the right pope for the cardinals, but not for the people. We were hoping for a South American, a Brazilian, a pope who would work for the neediest and the rights of women and children."

Niels Hendrich, 40, of Hamburg, Germany, jumped up and down at the prospect of a new pope — but then gave only three halfhearted claps when he learned who it was.

"I am not happy about this at all," he said. "Ratzinger will put the brakes on all the progressive movements in the church that I support."

At the sound of the bells, nuns pulled up their long skirts and joined others jogging toward St. Peter's Square to watch the new pope emerge. Many were delighted when Chilean Cardinal Jorge Arturo Medina Estivez stepped onto the balcony and announced Ratzinger's election.

"The cardinals elected a good and holy man who was close to Pope John Paul II," said Mark Wunsch, 27, a religious philosophy student from Denver. "He'll be a wonderful and good leader in preaching the truth and love."

If the new pope was paying tribute to the last pontiff who held the name Benedict, it could be interpreted as a bid to soften his image as the Vatican's doctrinal hard-liner.

Benedict XV — who reigned from 1914 to 1922 — was a moderate following Pius X, who had implemented a sharp crackdown against doctrinal "modernism." Benedict XV was pope during World War I, was credited with settling animosity between traditionalists and modernists and dreamed of reunion with Orthodox Christians.

Benedict, which comes from the Latin for "blessing," is one of a number of papal names of holy origin — such as Clement ("mercy") and Pius ("pious").

Observers said the new pope's age was a factor among cardinals who favored a "transitional" pontiff 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.

The new pope is the oldest elected since Clement XII, who was chosen in 1730 at 78 but was three months older than Ratzinger.

Cardinals also had faced a choice over whether to seek a younger, dynamic pastor and communicator — perhaps from Latin America or elsewhere in the developing world where the church is growing.

The last pope from a German-speaking land was Victor II, bishop of Eichstatt, who reigned from 1055 to 1057.

Some have questioned whether the new pope betrayed any pro-Nazi sentiment during his teenage years in Germany during World War II.

In his memoirs, he wrote of being enrolled in Hitler's Nazi youth movement 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.

Two years later, he was drafted into a Nazi anti-aircraft unit as a helper, a common fate for teenage boys too young to be soldiers. Enrolled as a soldier at 18, in the last months of the war, he barely finished basic training.

"We are certain that he will continue on the path of reconciliation between Christians and Jews that John Paul II began," Paul Spiegel, head of Germany's main Jewish organization, told The Associated Press in a telephone interview.

Less than an hour before Ratzinger's name was revealed, white smoke poured from the chimney atop the Sistine Chapel (search) in Rome, signaling that a new pope had been elected by the Vatican's College of Cardinals.

“My dearest brothers and sisters,” said Chilean Cardinal Jorge Arturo Medina Estivez from the balcony. "I announce to you a great joy. We have a pope!”

At about 6 p.m. local time, their eyes glued to the chimney, the crowd lingering in St. Peter’s Square (search) cheered, clapped, laughed and honked horns as the white smoke wafted out.

At first, no bells rang, as they were expected to when a pope had been decided upon, so there was some initial confusion as to whether the cardinals had settled on a choice.

But then the Sistine Chapel's big bell began tolling, signaling that the Vatican (search) had elected its next leader. The crowd went wild, waving flags and shouting in glee.

Earlier Tuesday, black smoke rose from the chapel, but several hours afterward, smoke again began pouring from the chimney as thousands watched from St. Peter's Square. Some couldn't tell whether it was black or white, but then people began to chant "It's white, it's white!" and minutes later the bells began tolling incessantly.

"Habemus papam, habemus papam," said Daomario Barbalho, 26, from Natal, Brazil, meaning in Latin "We have a pope."

Some were surprised that the next pope was decided upon so quickly.

Pope Pius XII was elected in 1939 in three ballots on one day, while Pope John Paul II was elected in 1978 in four ballots in two days. Benedict XVI was elected Tuesday after either four or five ballots over two days.

The two morning ballots Tuesday followed an early Mass in the cardinals' high-security Vatican hotel.

On Monday evening, black smoke that initially looked light enough to throw even Vatican Radio analysts off-guard poured from the chimney, disappointing a crowd of 40,000 pilgrims anxious for a sign that the cardinals had settled on a successor. That first puff followed the conclave's initial vote.

The cardinals had a staggering range of issues to juggle as they chose the first new pope of the 21st century — fallout from priest sex-abuse scandals and chronic shortages of priests and nuns, as well as calls for sharper activism against poverty and easing the ban on condoms to help combat AIDS.

The next pontiff also must maintain the global ministry of John Paul, who took 104 international trips in his more than 26-year papacy.

"We look forward to working with His Holiness and the Holy See to build upon our already excellent bilateral relationship and to promote human dignity across the world," said Adam Ereli, deputy State Department spokesman.

The first conclave of the new millennium was held amid unprecedented security, with the cardinals seated atop a false floor concealing electronic jamming devices designed to thwart eavesdroppers by cutting signals to cell phones or bugs.

It is also the first time in more than a generation that crowds have been staring at the chimney for the famous smoke and word of a new pope. In that time, the church has been pulled in two directions: a spiritual renaissance under John Paul, but battered by scandals and a flock pressing for less rigid teachings.

Before the conclave began, Ratzinger tried to set a tone of conservatism and urgency, warning cardinals, bishops and others gathered in St. Peter's Basilica for the Monday Mass that the church must stay true to itself.

About five hours later, the electors walked in a procession into the chapel decorated with frescoes by Michelangelo (search). They bowed before the altar and took their places.

For 30 minutes, each walked up and placed his right hand — with the special gold ring of the cardinals — on the Holy Book and again pledged never to reveal what would occur in the conclave. The penalty is severe: excommunication.

No conclave in the past century has lasted more than five days, and the election that elevated Polish Cardinal Karol Wojtyla (search) into the papacy as John Paul II in October 1978 took eight ballots over three days.

FOX News' Catherine Donaldson-Evans and The Associated Press contributed to this report.