The National Conference of Catholic Bishops in the USA has a collection of statements by religious leaders around the world regarding Iraq.Most of these statements from the Vatican and other national Bishop’s Conferences were made prior to the formal commencement of war.
However, the collection does include excerpts from the Pope’s statements after the formal commencement of hostilities.
http://www.nccbuscc.org/sdwp/peace/quotes.htm
http://www.nccbuscc.org/sdwp/peace/churchleaders.htm