Pope Francis said on Saturday that he hoped an upcoming global encounter at the Vatican would be a propitious time of unity and fraternity and not cause further polarisation in the Catholic Church.

The 86-year-old pontiff spoke at an ecumenical prayer vigil attended by leaders of various Christian Churches in St. Peter’s Square ahead of the opening on Wednesday of major month-long meeting in the Vatican, known as a synod, that could chart the Church’s future.

“Let us ask that the synod be a ‘kairos’ of fraternity, a place where the Holy Spirit will purify the Church from gossip, ideologies and polarization,” he said, using the ancient Greek word roughly meaning an opportune or critical moment to do something of significance.

About 18,000 people, mostly young Christians from around the world, attended, reading prayers for victims of war, injustice and sexual violence and calling for defence of the environment. Hundreds were later starting a three-day retreat north of Rome ahead of the opening of the synod.