(CNN) — Organizers of a key Vatican summit on clergy sexual abuse met with abuse survivors from around the world on Wednesday, saying afterward that the meeting will help them “better understand the gravity and urgency of the difficulties” church leaders will face during the four-day summit.

The meeting lasted for about two hours, according to a Vatican statement, and included 12 clergy abuse survivors from around the world.

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“The members of the committee are very grateful to the victims who participated for their sincerity, the depth and the strength of their testimonies, which will certainly help them to always better understand the gravity and urgency of the difficulties that they will confront during the course of the meeting,” the Vatican said in a statement.

Juan Carlos Cruz, a Chilean abuse survivor who helped organize the encounter, said it was attended by four members of the organizing committee for the Meeting of the Protection of Minors, including Cardinal Blase Cupich of Chicago, Cardinal Oswald Gracias of Mumbai, Archbishop Charles Scicluna of Malta and the Rev. Hans Zollner, a German Jesuit who is president of the Center for the Protection of Minors at the Pontifical Gregorian University.

“I felt that they had a open mind and that they sincerely want something to happen,” Cruz told CNN.

The 12 abuse survivors, including representatives from the groups Ending Clergy Abuse, the Survivors Network of those Abused by Priests and BishopAccountability.org, shared their experiences of abuse, Cruz said.

“And then there was a dialogue. Sometimes it got a bit intense, but there was a climate of respect.”

Cruz said the intensity in the room at the Institute Maria Bambina in Vatican City ratcheted up when some clergy abuse survivors pressed church officials on what actions they will take during the four-day summit that begins on Thursday.

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Peter Isely of the group Ending Clergy Abuse, who also attended the meeting, said he was disappointed that Pope Francis was not there, though the Pope has met several times previously with abuse survivors.

Isely also said he demanded that church officials adopt a “zero tolerance” policy for clergy abusers and bishops who fail to protect children.

“We made our demands and we think that’s the demands of not just survivors but for people everywhere: zero tolerance,” Isely said.

For the first time in Catholic history, nearly 200 church leaders from around the world, including more than 100 bishops, will gather at the Vatican starting Thursday to confront the scourge of clergy who sexually abuse children.

The unprecedented four-day summit, convened by Pope Francis last September, will include two speeches by the Pope, talks outlining best practices, small group discussions among bishops and a penitential ceremony involving abuse survivors.

The meeting comes as the Catholic Church is confronting a growing number of scandals, from priests and bishops accused of sexually abusing nuns to a salacious new book to be published Thursday that calls the Vatican “one of the biggest gay communities in the world” in which clergy regularly break their vows of celibacy.

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