ROME (CNN) -- The process of picking a new pope was one step closer to starting on Monday, as more than 140 Catholic cardinals began a meeting at the Vatican.
The cardinals gathered on Monday morning, but haven't yet decided when the conclave to select Pope Benedict XVI's successor will start, Vatican spokesman the Rev. Federico Lombardi told reporters.
"It's on the table, but no decision has been reached," Lombardi said.
The General Congregations meeting is a key step before the conclave, when all cardinals under age 80 meet at the Vatican to vote for the next pope.
Lombardi said 142 cardinals attended Monday morning's session. Of that group, 103 were cardinal electors who will choose the next pope. Twelve cardinal electors have not yet arrived in Rome, but were expected to arrive later Monday and Tuesday, he said.
At the Monday morning meeting, the cardinals recited an opening prayer, took an oath and discussed the timetable for the coming days, Lombardi said. A second meeting was planned for Monday afternoon.
Benedict stepped down on Thursday, after announcing on February 11 that he would resign. He was the first pope to resign in 600 years. Throughout history, the transfer of papal power has almost always happened after the sitting pope has died.
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 slightly amended the 500-year-old policy on pope selection to get a successor into place more rapidly.
The cardinals may to be able to pull it off before March 15, Lombardi has said.
This would give the new pontiff a little over a week to prepare for the next Mass, the Palm Sunday celebrations on March 24.
Some gambling houses in Europe are offering odds on who will become the next head of the Catholic Church.
The favorites include Archbishop Angelo Scola and Cardinal Tarcisio Bertone of Italy. They also include Cardinal Peter Turkson of Ghana, who could become the first African pontiff since Pope Gelasius I died more than 1500 years ago; and Cardinal Marc Ouellet of Canada, who could become the first North American pope.
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 acknowledging any specific incident. "To those I have offended, I apologize and ask forgiveness," he said in a statement.
The Vatican refused to answer questions on Monday about whether it will take any disciplinary action against O'Brien. In response to questions from British journalists, Vatican spokesman the Rev. Thomas Rosica read the statement that O'Brien released on Sunday.
"That is all we can say, is what's been said," Rosica said.
While Benedict won't be directly involved in his successor's selection, his influence will undoubtedly be felt. He appointed 67 of at least 115 cardinals set to make the decision.
Cardinals must vote for the pope in person, via paper ballot only. While some work at the Vatican, most are spread out worldwide running dioceses or archdioceses, and would have to travel to Rome.
Once the process begins, the cardinals aren't allowed to talk with anyone outside of the conclave. And they can't leave until the voting is done, and the telltale white smoke emerges from the Vatican chimney, letting the world know the conclave has agreed on a new leader.
When it does, there could be thousands of journalists watching.
Lombardi said Monday that 4,300 journalists have been accredited to cover the papal conclave.
-- CNN's Richard Allen Green reported from Rome. CNN's Mark Morgenstein reported from Atlanta. CNN's Catherine E. Shoichet contributed to this report.
™ & © 2013 Cable News Network, Inc., a Time Warner Company. All rights reserved.