Argentine flags greeted the former cardinal Jorge Mario Bergoglio as he recited the traditional Sunday Angelus prayer for the first time as Pope Francis and blessed a huge crowd at St. Peter's Square, breaking tradition once again while preaching on forgiveness.

"Thank you for your welcome, and for your prayers," the first Latin American pope said from his papal apartment above the square. "Pray for me."

Pope Francis had delivered off-the-cuff remarks in Italian about God's power to forgive instead of reading from a written speech for the first Sunday mass earlier.

Vatican Radio reported there were 300,000 people to greet the pontiff when he went out onto his balcony above St. Peter's Square.

"We ask for the grace of never tiring of asking pardon, for He never tires of pardoning," said the pontiff.

After his first papal Sunday Mass, the Pope stepped out of the St. Anne's church, a parish church for people working at the Vatican, past a security barrier and greeted parishioners individually in the fashion of a local pastor.

Children shouted his name, "Francesco! Francesco!"

On March 19, the Pope will celebrate his inaugural papal mass.

Less than two week after Benedict XVI became the first pope to step down voluntarily in 600 years, Francis was elected pontiff on March 13.

On March 23 Francis will fly by helicopter to Castel Gandolfo, a lakeside town south of Rome, and have lunch with Pope Emeritus Benedict, the Vatican announced Sunday.

XVI resigned, the first pope to do so in 600 years.

The Pope issued his first tweet from his Twitter@Pontifex account saying, "Dear friends, I thank you from my heart and I ask you to continue to pray for me. Pope Francis."

Later from his balcony mercy was again the theme of his homily which delighted the crowd.

He told a story, of an elderly widow he encountered during a Mass for the sick celebrated in connection with a visit of the image of Our Lady of Fatima.

"I went to confession during the Mass, " he said, " and near the end – I had to go to do confirmations afterward, and an elderly lady approached me - humble [she was] so very humble, more than 80 years old.

"I looked at her, and said, 'Grandmother,' – where I come from, we call elderly people grandmother and grandfather – 'would you like to make your confession?' 'Yes,' she said – and I said, 'but, if you have not sinned…' and she said, 'we all have sinned.'

"[I replied], 'if perhaps He should not forgive [you]?' and, sure, she replied, 'The Lord forgives everything.' I asked, 'How do you know this for sure, madam?' and she replied, 'If the Lord hadn't forgiven all, then the world wouldn't [still] be here.'

"And, I wanted to ask her, 'Madam, did you study at the Gregorian (the Pontifical Gregorian University, founded in 1551 by St Ignatius Loyola, the oldest Jesuit university in the world)?' – because that is wisdom, which the Holy Spirit gives – interior wisdom regarding the mercy of God.

"Let us not forget this word: God never tires of forgiving us," he repeated, " but we sometimes tire of asking Him to forgive us." Pope Francis went on to say, "Let us never tire of asking God's forgiveness."