The service yesterday evening in St Paul Outside the Walls Basilica capped a week of efforts in Rome and worldwide to foster unity among Christians.
The pope told participants that divisions among Christians impair the work of spreading the Gospel in the world. He urged Christians to humbly continue "on the way to the restoration of full visible unity."
Francis also prayed for God's help in overcoming "our conflicts, our divisions and our self-seeking," which he described as obstacles to unity.