I thought the Vatican made an announcement that there were to be no "prayers" offered at this ecumenical gathering of false religions. Whatever Pope Benedict XVI says, his actions clearly show his intentions.
That those outside the Roman Catholic Church seeking "truth" and peace (as the pontiff says) are our brothers and therefore members of the "universal church."
This has been condemned by Pope St Pius XII in his encyclical,
Mystici Corporis. Also condemned by Vatican Council I: "
"If anyone should say, that the true Church is not one body in itself, but consists of varied and diverse societies of Christian name, and is spread out among them, or that various societies disagreeing among themselves in profession of faith and separated by communion, constitute, as members or parts, the one and universal Church of Christ, let him be anathema."

Read the Vatican II documents and then read teachings of the Church Fathers in regards to religious liberty, the liturgy, and ecuminsim.