Cardinals also imposed a media ban to help them concentrate on the task of choosing the next pope, Vatican spokesman Joaquin Navarro-Valls said.
They unanimously decided not to speak to the media during a period of "more intense prayer" as they prepare for the secret conclave starting on April 18, he said.
The number of cardinals involved in the conclave was cut to 115, after the Vatican announced a second cardinal had been struck down by illness and could not attend.
Meanwhile, the head priest of Saint Peter’s Basilica, Monsignor Francesco Marchisano, said the next pope should be stamped with the "infinite humanity" of John Paul II.
Marchisano presided over a solemn Mass in memory of the pontiff, one of the so-called "Novendiales" Masses signifying nine days of mourning following the death of a pope.
Homilies delivered during these Masses are traditionally scrutinized for signals of Vatican thinking about the qualities desirable in a papal successor.
"I saw a man who knew how to understand, to share, the walks with others," Marchisano, 75, told a congregation of some 2,000 cardinals, dignitaries, journalists and ordinary people. John Paul II "knew how to understand, to participate, to thank. He knew how to walk with others, I believe that’s one of the superior qualities which our dear pope had."
"How many times did he walk with others, in the various nations where there were problems, always to find a solution," he said.
Among those at the Mass were Italian "papabile" Giovanni Battista Re and the late pope’s private secretary Archbishop Stanislaw Dziwisz.
Friday’s funeral Mass for John Paul II was briefly interrupted when many in the massive crowd of mourners began chanting "santo, santo" repeatedly, while others held up large banners demanding "santo subito" (sainthood now).
Answering a question at a news conference, Navarro-Valls said any decision to canonize John Paul II lay "in the sole competency" of his successor.
He was speaking after cardinals convened for their sixth meeting since the pope died a week ago, a series broken only for the ritual of the funeral.
South African cardinal Wilfrid Fox Napier said as it ended that they were preparing for the conclave and would not comment.
A total of 130 cardinals out of 183 are now in Rome.
However, only 117 are eligible to vote by virtue of being under the age of 80, and Navarro-Valls said Cardinal Adolfo Antonia Suarez Rivera of Monterrey, Mexico, was unable to attend for health reasons. Manila’s Jaime Cardinal Sin will also be absent.
All but two of the cardinals who will be voting for his successor were appointed by John Paul II.
In Rome, Mayor Walter Veltroni said the city’s main rail station is to be named after the late pontiff.
He said that after a new pope is named, authorities will consult with the Vatican on how to give it a look that "strongly recalls the message of a pope who was the pontiff of awareness, dialogue and travel."
Following the scores of world leaders who flew out of Rome after the funeral, tens of thousands of ordinary mourners also packed trains, planes and coaches out of the city.
Authorities estimate about one million people filled Saint Peter’s Square and surrounding streets for the requiem Mass and that over two million arrived in the Italian capital overall since the pope’s death.
Rail authorities said 200 special trains were put into service on Saturday alone to help them get away again.
"The entire country, all of Italy, should be proud of its capital," Veltroni said, adding he had received congratulatory telephone calls from his New York counterpart Michael Bloomberg as well as Italian leaders.
Saint Peter’s Basilica, where hundreds of thousands of mourners filed past the pope’s body lying in state, reopened to tourists for the first time in five days, although the crypt containing his tomb will stay shut until next week.