Victims expected 'concrete and efficient measures' to address the abuse and scandal and not mere condemnations, Francis said in a short opening statement.
The unprecedented four-day meeting, starting on Thursday, brings together presidents of national Roman Catholic bishops conferences, Vatican officials, experts and heads of male and female religious orders.
Cardinal Gerhard Mueller, 71, a German who was the Vatican's doctrinal chief until 2017, issued the four-page manifesto on Friday via conservative Catholic media outlets.
Francis made his comments on the plane returning from Abu Dhabi in response to a reporter's question about an article last week in a Vatican monthly magazine about the abuse of nuns in the Catholic Church.
'If you are with Jesus, if you love to listen to his word as the disciples of that time did, if you try to live out this word every day, then you are blessed.'
In Dubai's overflowing churches and Riyadh's secretive masses, Catholics across the Gulf are eagerly awaiting Pope Francis' historic visit to the United Arab Emirates next week.