While Benedict won't be directly involved in his successor's selection, his influence will undoubtedly be felt. He appointed 67 of the 117 cardinals that -- as of Monday -- are set to make the decision.

The number of electors could drop to 115, as two cardinals will turn 80 in March, when their age makes them ineligible to cast a vote. More than two-thirds of the final number of cardinals must agree on the next pope. The announcement that a decision has been made will come in the form of a puff of white smoke emerging from a chimney in the Vatican.

The Vatican does not formally invite cardinals to come to Rome for a conclave to elect a new pope, Lombardi said Tuesday.

"The cardinals are intelligent people. They know to come," he said, adding that he expected them to arrive during the first two weeks of March.

Much speculation has focused on whether Benedict's successor might come from Africa or Latin America, rather than Europe, where Roman Catholic congregations are shrinking.

Ratzinger said he expected to see a pope chosen from outside Europe one day -- but not just yet.

"I'm certain a pope will come from the new continents but whether it will be now, I have my doubts," he said. "In Europe, we have many very able people, and the Africans are still not so well known and maybe do not have the experience yet."

Bets are already being placed on which of the cardinals might step into Benedict's shoes.

Perhaps belying Ratzinger's prediction, UK bookmaker William Hill has Canadian Marc Ouellet and Ghanaian Mark Turkson are showing as favorites so far, at 7-2 odds.

Close behind are the Archbishop of Milan, Cardinal Angelo Scola, at 5-1 and Argentina's Leonardo Sandri, at 7-1. There are odds of 33-1 on New York's Timothy Dolan becoming pope.

Whoever gets the nod, the selection of a new pontiff is expected to go smoothly.

"We're not going to have a problem of two competing popes. If Pope Benedict still wanted to have influence, he wouldn't have stepped down," said senior Vatican communications adviser Greg Burke.

"What's interesting is how long ago this decision was made -- shortly after the pope's trip to Cuba, which was in March of last year, so that was before the whole butler story even broke."

The pope's butler, Paolo Gabriele, was convicted in a Vatican court last year on charges of leaking private papers from the Vatican. He was sentenced to 18 months in prison but was pardoned weeks later.

The leaked papers revealed claims of corruption in the church's hierarchy.

As an aside, Lombardi referred to concerns over financial oversight in the city state, which have meant that Vatican shops and museums have not been able to accept credit or debit cards since January 1.

"The credit card payments in the state of the Vatican city are again working, and so the pilgrims as well as the tourists who visit the church of St. Peter's every day can now use the ordinary payment service, including paying for the Vatican museums," Lombardi said.

The payment service is guaranteed by Swiss firm Aduno, he said.

"Thus, even though the pope has resigned, things get done," he added.

Filipino iReporter Rummel Pinera says Benedict's decision to resign should prompt wider debate about how long pontiffs should serve.