During Sunday’s homily in Spanish, the 78-year-old Argentine pontiff called the crowd to be open to “miracles of love for the sake of all the families of the world”.
“The urgent challenge of protecting our home includes the effort to bring the entire human family together in the pursuit of a sustainable and integral development, for we know that things can change.”
And finishing Mass, the Pope said: “I ask you to pray for me. Don’t forget.”
Earlier on Sunday, he met the five victims, all now adults who had suffered sexual abuse as children, during a seminary in Pennsylvania.
The group – three women and two men – had been abused by clergy, family members or teachers, papal spokesman Father Federico Lombardi said in a statement.
He said the Pope was “overwhelmed with shame that men entrusted with the tender care of children violated these little ones and caused grievous harm”.
Francis told the victims who were abused by a member of the clergy that he was “deeply sorry” for the times when the abuse was reported, but victims or their families “were not heard or believed,” the statement said.
It added that the Pope “renewed his commitment” to ensure that victims are treated with justice, the guilty are punished, and to effective prevention in the Church and in society, the statement said.
But survivors’ advocacy groups expressed some scepticism at whether the Pope’s words would lead to any change.
John Salveson, President of the Pennsylvania-based Foundation to Abolish Child Sex Abuse, said: “The truth is that the survivor community has been asking the Church to take several simple steps to protect children and hold perpetrators and enablers accountable for years, but the Church has refused to take these actions.
“If Pope Francis wishes to take effective action to back up his words he could take these steps immediately.”
In June the Pope approved the creation of a tribunal to hear cases of bishops accused of covering up child abuse by paedophile priests.
Last year, the UN strongly criticised the Church for failing to stamp out abuse and for allowing cover-ups.