Standing ovation, tears at Pope Benedict's final public Mass

"Thank you. Now, let's return to prayer," the 85-year-old pontiff said, bringing an end to several minutes of applause that clearly moved him. In an unusual gesture, bishops took off their mitres in a sign of respect and a few of them wept.

One of the priests at the altar, which according to tradition rests above the tomb of St Peter, took out a handkerchief to dry his tears.

The Mass was moved to St Peter's from a venue in Rome so more people could attend. Hundreds of others waited outside.

Hours earlier in the Vatican's modern audience hall, a visibly moved Benedict tried to assure his worldwide flock, saying he was confident his decision to step down would not hurt the Church.

The faithful watch the Ash Wednesday Mass led by Pope Benedict XVI on a giant screen in St. Peter's Square

The Vatican, meanwhile, announced that a conclave to elect his successor would start sometime between March 15 and March 20, in keeping with Church rules about the timing of such gatherings after the papal see becomes vacant.

"Continue to pray for me, for the Church and for the future pope," he said in unscripted remarks at the start of his weekly general audience, his first public appearance since his shock decision on Monday that he will step down on Feb. 28.

It was the first time Benedict, 85, who will retire to a convent inside the Vatican, exchanging the splendour of his 16th century Apostolic Palace for a sober modern residence, had uttered the words "future pope" in public.

Church officials are still so stunned by the move that the Vatican experts have yet to decide what his title will be and whether he will continue to wear the white of a pope, the red of a cardinal or the black of an ordinary priest.

His voice sounded strong at the audience but he was clearly moved and his eyes appeared to be watering as he reacted to the thunderous applause in the Vatican's vast audience hall, packed with more than 8,000 people.

In brief remarks in Italian that mirrored those he read in Latin to stunned cardinals on Monday he appeared to try to calm Catholics' fears of the unknown.

He message was that God would continue to guide the Church.

EXAMINATION OF CONSCIENCE

"I took this decision in full freedom for the good of the Church after praying for a long time and examining my conscience before God," he said.

He said he was "well aware of the gravity of such an act," but also aware that he no longer had the strength required to run the 1.2 billion member Roman Catholic Church, which has been beset by a string of scandals both in Rome and round the world.

Benedict said he was sustained by the "certainty that the Church belongs to Christ, who will never stop guiding it and caring for it" and suggested that the faithful should also feel comforted by this.

He said that he had "felt almost physically" the affection and kindness he had received since he announced the decision.

When Benedict resigned on Monday, the Vatican spokesman said the pontiff did not fear schism in the Church after his resignation.

Some 115 cardinals under the age of 80 will be eligible to enter a secret conclave to elect his successor.

Cardinals around the world have already begun informal consultations by phone and email to construct a profile of the man they think would be best suited to lead the Church in a period of continuing crisis.

The conservative Benedict has appointed more than half of the cardinals who will elect his successor so it is unlikely the new man will tamper with any teachings such as the ban on artificial birth control or women priests.

But many in the Church have been calling for the election of someone who they say will be a better listener to other opinions in the Church.

The likelihood that the next pope would be a younger man and perhaps a non-Italian, was increasing, particularly because of the many mishaps caused by Benedict's mostly Italian top aides.

Benedict has been faulted for putting too much power in the hands of his friend, Secretary of State Cardinal Tarcisio Bertone. Critics of Bertone, effectively the Vatican's chief administrator, said he should have prevented some papal mishaps and bureaucratic blunders.

ILL-SERVED POPE

"These scandals, these miscommunications, in many cases were caused by Pope Benedict's own top aides and I think a lot of Catholics around the world think that he was perhaps ill-served by some of the cardinals here," said John Thavis, author of a new book, The Vatican Diaries.

Benedict's papacy was rocked by crises over sex abuse of children by priests in Europe and the United States, most of which preceded his time in office but came to light during it.

His reign also saw Muslim anger after he compared Islam with violence. Jews were upset over rehabilitation of a Holocaust denier. During a scandal over the Church's business dealings, his butler was accused of leaking his private papers.

"When cardinals arrive here for the conclave ... they are going to have this on their mind, they're going to take a good hard look at how Pope Benedict was served, and I think many of them feel that the burden of the papacy that finally weighed so heavy on Benedict was caused in part by some of this in-fighting (among his administration)," Thavis told Reuters.

Vatican spokesman Father Federico Lombardi urged the faithful to remain confident in the Church and its future.

"Those who may feel a bit disorientated or stunned by this, or have a hard time understanding the Holy Father's decision should look at it in the context of faith and the certainty that Christ will support his Church," Lombardi said.

Lombardi said that on his last day in office, Benedict would receive cardinals in a farewell meeting and after Feb. 28 his ring of office, used to seal official documents, would be destroyed just as if he had died.