Vatican City:
Pope Benedict XVI made his first public appearance on Wednesday since the shock announcement of his resignation, sticking with his schedule by presiding over his weekly general audience.
Tickets to the event in the Vatican's Paul VI auditorium were issued well in advance, so several thousand pilgrims experienced the historic moment out of sheer luck just two days after the 85-year-old Benedict said he would step down at the end of the month.
The pope will then celebrate Ash Wednesday mass at 1600 GMT, his last public mass and one of his final engagements as pontiff.
The mass is traditionally held in the Santa Sabina Church on Rome's Aventine Hill, but has been moved to St Peter's Basilica out of respect for the outgoing pontiff and to accommodate the crowd of faithful who will want to mark the end of his eight-year rule -- one of the shortest in the Church's modern history.
"It will be an important concelebration, and the last led by the Holy Father in Saint Peter's," Vatican spokesman Federico Lombardi said.
The high point of Wednesday's mass, which launches the traditional period of penitence ahead of Easter in the Christian calendar, will see the pope mark the foreheads of the faithful with ashes.
Lombardi has said he expects a new pope in place in time for Easter, which falls on March 31 this year, although no date has yet been set for the secret conclave to elect a new leader of the world's 1.2 billion Catholics.
In the meantime, the outgoing pontiff will honour his existing engagements.
On Thursday he will hold his annual meeting with the pastors of Rome. And before he steps down at the end of the month he will also meet the presidents of Guatemala and Romania, as scheduled.
Next week will be given over to a spiritual retreat at the Vatican which is sure to be dominated by jockeying among factions within the College of Cardinals over the choice of Benedict's successor.
Benedict's decision to step down -- making him the first pontiff in 700 years to resign simply because he cannot carry on -- sparked a flurry of rumours over his health, fed by revelations that he had had an operation to replace the batteries in his pacemaker three months ago.
Some observers saw Benedict's decision as a bid to avoid the fate of his predecessor John Paul II, whose drawn-out and debilitating illness was played out on the world's stage.
But Lombardi insisted: "The pope is well and his soul is serene.
"He did not resign the pontificate because he is ill but because of the fragility that comes with old age."
After Ash Wednesday Benedict will, on the next two Sundays, will recite the Angelus from his apartment window and hold his final general audience, this time in St. Peter's Square on February 27, before retiring to a little-known monastery within Vatican walls.
Soon a new pope will be installed in the papal apartments, with his predecessor just a stone's throw away.
But Benedict will spend his time in prayer rather than giving advice, the Vatican says.
As rumours fly over front-runners for St. Peter's chair, commentators have said age may be a key factor in selecting a new pope, although any of the 117 cardinals eligible to vote is likely to be chosen.
While some hope Africa or Asia could yield the next pontiff, others have tipped high-flying European or North American cardinals. The new pope will have to face up to the growing secularism in the West, one of the Church's biggest challenges.
Only one other pope has resigned because of an inability to carry on -- Celestine V in 1294 -- a humble hermit who stepped down after just a few months saying he could no longer bear the intrigue of Rome.