Normally, the College of Cardinals is not allowed to select a new pontiff until 15 to 20 days after the office becomes vacant. However, Benedict amended the 500-year-old policy to get a successor into place more rapidly.
The cardinals may to be able to do so before March 15, Lombardi has said.
This would give the new pontiff more than a week to prepare for the March 24 Palm Sunday celebrations.
Some gambling houses are offering odds on who will next lead the Catholic Church.
Favorites include the archbishop of Milan, Italy, Cardinal Angelo Scola; Cardinal Tarcisio Bertone of Italy; Cardinal Peter Turkson of Ghana, who would become the first African pontiff since Pope Gelasius I died more than 1,500 years ago; and Cardinal Marc Ouellet of Canada, who would become the first North American pope.
While Benedict has no direct involvement in the selection of his successor, his influence will be felt: He appointed 67 of at least 115 cardinals set to make the decision.
Wounded 'hearts and minds'
One former cardinal who won't participate in the conclave is Keith O'Brien of Scotland, who resigned last month. O'Brien apologized Sunday for sexual impropriety, without specifying any incident.
"To those I have offended, I apologize and ask forgiveness," he said in a statement.
The Vatican refused to answer questions Monday about whether it would discipline O'Brien.
But others did comment.
"It looks as if the incidence of abuse is practically zero right now as far as we can tell, but they are still the victims, and the wound therefore is deep in their hearts and minds very often," Cardinal Francis George, archbishop of Chicago, told reporters in Rome. "As long as it's with them, it's with all of us. And that will last for a long time, so the next pope has to be aware of this."
Philip Tartaglia, the archbishop of Glasgow and apostolic administrator of the Archdiocese of St. Andrews and Edinburgh, will administer O'Brien's archdiocese until a new appointment is made.
"The most stinging charge which has been leveled against us in this matter is hypocrisy, and for obvious reasons," Tartaglia said Monday night in a sermon at St. Andrew's Cathedral in Glasgow. "I think there is little doubt that the credibility and moral authority of the Catholic Church in Scotland has been dealt a serious blow, and we will need to come to terms with that."
Representatives of a support group for abuse victims, Survivors Network of those Abused by Priests, or SNAP, called Monday for the cardinals to elect a new pope who is not a Vatican insider.
The group also called for some of the older cardinals to absent themselves from the General Congregations, arguing that some have been accused of complicity in protecting priests accused of sexually abusing children.
"Their peers should push them to stay home, or they should do so voluntarily, the group feels, for the sake of the church and to avoid heaping more pain on wounded victims and betrayed Catholics," a statement on SNAP's website said.
One of Italy's anti-clerical abuse networks, L'Abuso, petitioned senior Vatican Cardinal Tarcisio Bertone on Monday not to allow the participation in the conclave of an Italian cardinal it alleges helped protect priests who molested minors in the past.
Cardinals must vote in person, via paper ballot. Once the process begins, the cardinals aren't allowed to talk with anyone outside of the conclave. They cannot leave until white smoke emerges from the Vatican chimney -- the signal that a new leader has been picked.
More than 5,000 journalists are now accredited for the papal conclave, Lombardi said Tuesday. They cover 24 languages, he said.