Greek-Melkite (Catholic) Archbishop Isidore Battikha, who is heading the committee preparing for the pope's May visit to Syria, said the pope will enter the historic Omayyad Mosque, where tradition says the head of St. John the Baptist is buried. There will be a joint Christian-Muslim prayer afterward outside the mosque, the archbishop said.
No sitting pope has ever before stepped into a mosque. During a trip to Jerusalem last year, John Paul did not enter the Al Aqsa Mosque, the third-holiest Islamic shrine, when he visited the Haram al-Sharif complex.
But John Paul has already been a pioneer in inter-religious contacts. He was the first pope to enter a synagogue, with his visit to Rome's main Jewish house of worship in 1986.
At the Vatican Tuesday, officials could not confirm the planned mosque visit, saying the pope's official program in Syria was not yet complete.
However, Zenit.org, a Vatican-affiliated news services, reported that the event "should take place May 6."
Zenit said the pope would enter the mosque "barefoot," as do all who enter a place of Muslim worship.
Despite Battikha's comments, reported by the Associated Press, Zenit said it was uncertain whether the pope would actually enter the premises consecrated to Muslim prayer.
The Omayyad Mosque stands on ground that has been holy to various groups since at least the ninth century B.C., when a people called the Aramaeans built a temple to their god Hadad. When the Romans ruled what is now Syria, the site was used as Jupiter's temple. After the Roman emperor Constantine adopted Christianity, it became a church dedicated to St. John the Baptist.
Christians who believe St. John's head is kept in a casket entombed in the mosque regularly visit what is one of the world's most popular Muslim pilgrimage sites.
Islam reached Syria in 636 and by the eighth century, rulers of the Omayyad converted the church into a mosque and had declared they would make the site the world's greatest Muslim place of worship.
Pope John Paul, who has been visiting biblical sites in recent years, is expected in Syria in early May on a tour that will include the Mediterranean island of Malta. St. Paul's travels took him to both Malta and Syria.
Last year, the pope visited Egypt, Jordan, Israel, and the Palestinian territories.