Cardinal Roger Mahony, the retired archbishop of Los Angeles, tweeted after meeting Benedict that he had asked Benedict to pray for the people of Los Angeles. "He grasped my hand and said 'Yes'!!" Mahony said.

The current Catholic archbishop in Los Angeles earlier this month disciplined Mahony for his mishandling of "painful and brutal" allegations of sexual abuse by priests. Mahony's decision to travel to Rome to take part in the election of the new pope has been controversial because of that.

DiNardo and O'Malley said they would pray for guidance in choosing the new pope.

"I consider it one of the most important activities that I will be engaged in as a priest and a cardinal," said O'Malley, for whom the conclave will be his first.

"I think the discussions that we will have in the congregations will be the most important intellectual preparation that we have -- certainly the spiritual preparation has already begun.

"Our people back home and throughout the world are all praying that we will be guided to be able to choose the very best person to lead us."

Twitter shutdown

Cardinals are forbidden to communicate with the outside world -- now including by Twitter -- during the conclave, held within the Sistine Chapel. There is no Internet access inside Santa Marta, where the cardinals will stay during the conclave, Lombardi said.

Cardinal Gianfranco Ravasi of Italy, tipped as a possible future pope, tweeted Thursday morning that he would be away for a few days.

A number of other cardinals, including Ghanaian Peter Turkson, also considered a frontrunner, and New York's Timothy Dolan are also present on Twitter.

Benedict, who will not be involved in the election, will not get any advance notice of who his successor will be, Roscia said. The pope emeritus will find out who has been elected at the same time as the rest of the world.

Cardinal Javier Lozano Barragan of Mexico, who turned 80 last month and so is not a cardinal-elector, would not be drawn to comment Wednesday on who the next pope might be.

As to whether the cardinals are talking to each other about it now, he told CNN: "There are contacts, of course there are contacts. But what people talk about, who knows?

"There is a saying in Rome: He who enters the conclave as a possible pope comes out a cardinal."

Mired in scandal

Benedict's resignation opens up the prospect of unforeseen opportunities and challenges for the Roman Catholic Church.

Many are wondering whether a new pontiff will choose to lead the church in a different direction -- and can lift it out of the mire of scandal that has bogged down this pope's time in office.

Even as Benedict's final week began, Vatican officials were trying to swat down unsavory claims by Italian publications of an episode involving gay priests, male prostitutes and blackmail. Then the news broke that Benedict had moved up the resignation of a Scottish archbishop linked over the weekend by a British newspaper to inappropriate relationships with priests.

Last year, leaks of secret documents from the pope's private apartment -- which revealed claims of corruption within the Vatican -- prompted a high-profile trial of his butler and a behind-doors investigation by three cardinals.

Their report, its contents known so far only to Benedict, will be handed to his successor to deal with, the Vatican said.