A four-hour prayer vigil in St. Peter's Square for peace in Syria, initiated by Pope Francis and to be held this Saturday, will be the largest the Vatican has seen in years, according to the Holy See's press director.

"I've been here for 23 years and I remember gatherings for peace in Assisi, but I don't remember anything with this dimension in Saint Peter's Square," Fr. Federico Lombardi told a gathering of journalists Sept. 5.

He recalled a peace gathering in Italy and prayer vigils held after the Sept. 11 attacks, but none were of the degree that this will be, he said.

Pope Francis made a global petition on Sept. 1 asking that everyone, regardless of religion or location, to fast and pray during the whole day of Sept. 7 for world peace, particularly in Syria.

"There are so many conflicts in this world which cause me great suffering and worry, but in these days my heart is deeply wounded in particular by what is happening in Syria and anguished by the dramatic developments which are looming," the Holy Father said Sept. 1.

During his first public general audience since his summer break on Sept. 4, he renewed his invitation.

While the Sept. 7 fast is not binding on the faithful, Pope Francis' repeated exhortations to participate in the fast indicate how close the issue is to the heart of the vicar of Christ.

His call for prayer and fasting comes as nations, including the United States, discuss the possibility of military intervention in Syria, following reports that the Bashar al Assad regime used chemical weapons on its own civilians, killing, according to the U.S. government, more than 1,400 persons.

Pope Francis' prayer vigil will be preceded by the hearing of Confessions, beginning in the evening at 5:45 in St. Peter's Square. There will be 50 priests available for Confession under the colonnades of the square.

Then at 6:30, Pope Francis' Sept. 1 allocution calling for the day of fasting and prayer will be read to introduce the vigil.

Pope Francis will begin the prayer at 7:00, and the Veni Creator Spiritus will be sung.

Four Swiss Guards will carry an icon of Mary, Protectress of the Roman People, starting from the obelisk in the square, accompanied by two youths with flowers.

The Roman Pontiff will then begin praying the rosary, invoking the intercession at each mystery of Our Lady, Queen of Peace.

There will then be a meditation by the Pope, followed by a minute of silence and Eucharistic Adoration.

The vigil will also include readings from the Bible, and responsorial prayers for peace.

After Adoration, there will be three minutes of silence followed by the recitation of the Office of Readings, part of the Liturgy of the Hours.

At 10:15 there will be a period of extended, prayerful silence, and the vigil will conclude later with Benediction, around 11:00.

In solidarity with the vigil of the Diocese of Rome, many Churches worldwide will be holding similar events.

The Archdiocese of Madrid announced that all Masses said this Saturday will be offered for peace in Syria, and Bishop Demetrio Fernandez Gonzalez of Cordoba asked that church bells be rung at noon to remind Catholics to pray the Angelus to Mary, Queen of Peace.

Cardinal Timothy Dolan, the Archbishop of New York, announced that the anticipated Mass at his cathedral on Sept. 7 would be said for the intention of peace in Syria, and added that in his diocese "I wish all our Catholic people to abstain from meat this Friday (Sept. 6), and add this intention to their prayers at Sunday Mass."

In the Archdiocese of Denver, a vigil of Adoration will be held at the cathedral on Sept. 7 from 7 p.m. until midnight.