VATICAN CITY - The pope's surprise announcement Monday that he will resign Feb. 28 sets the stage for a battle that is likely to determine the future course of a church troubled by declining faith in its traditional strongholds.

Citing advanced years and infirmity, Benedict XVI became the first pope in six centuries to resign. Vatican officials said they hope to have a new pope in place by Easter, while expressing shock at the German's decision.

Saying he had examined his conscience "before God," Benedict said he is no longer up to the challenge of guiding the world's 1 billion Catholics. The next pope - Benedict was elected to the papacy in 2005 - will have to contend not only with a Roman Catholic Church still marred by the sexual abuse crisis, but also with an increasingly secular Europe and the spread of Protestant evangelical movements in the United States, Latin American and Africa.

The resignation sets up a struggle between the staunchest conservatives, in Benedict's mold, and those who feel the church can best widen its appeal in small but significant ways, such as allowing divorced Catholics to receive communion or loosening restrictions on condom use.

There are no plausible candidates who would move on issues such as the ordination of women or ending celibacy for priests.

The other big battle in the church is over the geography of Catholicism, which has spread decisively to the developing world. Today, 42 percent of its adherents come from Latin America and about 15 percent from Africa, versus only about 25 percent from Europe. That has led many to say that the new pope should represent a part of the world where membership is growing quickly.

Although most of the world's Catholics live outside Europe, most of the cardinals come from Europe.

DIFFERENT PROCEDURE

Under normal circumstances, the cardinals would descend on Rome after the death of the reigning pope. In this case, said the Vatican spokesman, the Rev. Federico Lombardi, the pope will carry out his duties until Feb. 28 at 8 p.m., with a successor probably elected by the end of March.

But he said the timing for an election of a new pope is "not an announcement; it's a hypothesis."

Already, speculation is rife about who best fills the perceived needs of the church.

• Cardinal Angelo Scola, the archbishop of Milan, is seen as the strongest Italian contender. A conservative theologian with an interest in bioethics and Catholic-Muslim relations, he is known for his intellect, his background in the same theological tradition as Benedict, his media savvy and his strong ties with the Italian political establishment. Vatican experts laud his popular touch.

• Cardinal Marc Ouellet, a dogmatic theologian and a Canadian, is widely seen as a favorite of Benedict, who named him head of the Vatican's influential Congregation for Bishops to help select bishops around the world. Critics in his native Quebec said that he was out of step with the province's more progressive bishops, but that is not necessarily a drawback in today's church.

• Cardinal Peter Appiah Turkson of Ghana, the head of the Vatican's Pontifical Council for Social Justice, is seen as the most likely African contender. Educated in Rome and New York, he is known for his semi-orthodox views on the use of condoms, saying that married couples could possibly use them to prevent infection where HIV is present.

• Cardinal Leonardo Sandri, the prefect for the Congregation for Eastern Churches, is an Argentine who would excite the Latin American wing of the church. He is also a skillful Vatican insider who served in the Secretariat of State under John Paul II and knows how to navigate the Vatican's complex bureaucracy, which might make him effective, experts say.

• During the Cold War it would have been a long shot, but for the first time there is talk that an American, Cardinal Timothy M. Dolan of New York, could be a contender. His deep conservatism combined with a folksy charisma make him popular with the faithful, at a time when the church is focused on "new evangelization."

A NEW DIRECTION?

Benedict was seen as a weak manager, and his papacy was troubled by debilitating scandals, most recently one in which his butler was convicted by a Vatican court in October of aggravated theft after he admitted stealing confidential documents, many of which wound up in a tell-all book.

His successor will have to contend with a range of staggering practical challenges, including a perennial shortage of priests and nuns worldwide, as well as a sexual abuse crisis that has undermined the church's moral authority, especially in Germany, the United States and other English-speaking countries.

Benedict has appointed 67 of the 118 cardinals who will appoint his successor, and 37 are from Europe, which remains the most substantial voting bloc. Nearly all of the 118 were appointed by Benedict and his predecessor, John Paul II, both strong traditionalists, and it is likely that the next pope will share their vision and doctrine.

With more than 150 million Catholics and a growing population, Africa represents one of the church's few avenues for expansion, and church leaders have assiduously promoted charismatic bishops and cardinals in nations such as Nigeria and Ghana. In 2002, Benedict, then Cardinal Joseph Ratzinger, spoke of the merits of electing an African pope.

Still, "there's a very strong likelihood that it will be someone from Europe," said the Rev. Thomas J. Reese, senior fellow at the Woodstock Theological Center at Georgetown University.