Organizers are desperate to get the "Mad Max" star on board because they believe Gibson's role in the celebrations could secure victory for Sydney in the battle to be the venue for the Catholic Church's World Youth Day in 2008.
Plans include holding the Last Supper at the famous Sydney Opera House ending with the crucifixion of Christ at St Mary's Cathedral.
The Archbishop of Sydney, George Pell, says, "He might well be attracted. I think his devotion to Christ is very real."
The venue for the event, expected to attract an estimated 400,000 young Catholics from 160 countries, will be announced by Pope Benedict XVI on August 21.