VATICAN CITY (AP) — Pope Francis has opened a divisive meeting of the world's bishops on family issues by forcefully asserting that marriage is an indissoluble bond between man and woman. But he says the church must "seek out and care for hurting couples with the balm of acceptance and mercy."

In a solemn Mass in St. Peter's Basilica on Sunday, Francis dove head-on into the most pressing issue confronting the meeting of 270 bishops: How to better minister to Catholic families experiencing separation, divorce and other problems.

He said: "The Church must search out these persons, welcome and accompany them, for a church with closed doors betrays herself and her mission and instead of being a bridge, becomes a roadblock."

One of the major debates at the synod is whether divorced and civilly remarried Catholics can receive Communion.