Pope Francis on Sunday hosts an unprecedented peace prayer meeting with Israeli President Shimon Peres and Palestinian leader Mahmud Abbas in a symbolic gesture to foster dialogue but unlikely to have any immediate effect.
Tensions are running high between the two sides following the formation of a new Palestinian unity government backed by the Islamist group Hamas and the announcement of Israeli plans for building 3,200 new settler homes.
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The Vatican is realistic about the effects of the ceremony.
"Nobody is fooling themselves that peace will break out in the Holy Land," said Father Pierbattista Pizzaballa, the head of the Franciscan Order in the Middle East who is organising the historic event in the Vatican Gardens.
"But this time to stop and breathe has been absent for some time," he said, after Francis made the offer to Peres and Abbas on a visit to the Middle East last month.
"The pope wants to look beyond, upwards," Pizzaballa said, adding: "Not everything is decided by politics."
Francis himself has been realistic about the prospects of his initiative, saying it would be "crazy" to expect any Vatican mediation in the Israeli-Palestinian conflict but adding that just praying together might help in some way.
In a tweet from the pope's @pontifex account on Saturday, Francis said: "Prayer is all-powerful. Let us use it to bring peace to the Middle East and peace to the world."
The Vatican has defined the meeting as an "invocation for peace" but has stressed it will not be an "inter-religious prayer", which would pose problems for the Christian, Jewish and Muslim communities taking part.
Peres is set to arrive at 1615 GMT followed shortly later by Abbas, with Francis welcoming them outside St Martha's Residence where he lives in the Vatican.
They will then go together to the Vatican Gardens, where the prayers will be recited in chronological order of the world's three main monotheistic religions, starting with Judaism, followed by Christianity and then Islam.
The prayers from each of the three delegations will focus on three themes: "creation", "invocation for forgiveness" and "invocation for peace", the Vatican said.
They will be read out in Arabic, English, Hebrew and Italian and will be accompanied by musical interludes.
Rabbi Abraham Skorka and Muslim professor Omar Abboud, two friends of Francis's from Buenos Aires who went with him on his trip to the Middle East will also attend.
Following the prayers, the pope and the two presidents will make their invocation for peace and the three will then plant an olive tree in a symbolic call for peace.
The Vatican called the event "a pause from politics".
Every detail about Sunday's meeting has been sensitive -- the explanation for the delay in publishing the composition of the delegations taking part.
Friday was excluded since it is a Muslim holy day and Saturday for the same reason for the Jewish community, while Sunday is Pentecost for Catholics -- a day of celebration of the Holy Spirit considered appropriate.
The choice of the Vatican Gardens is also significant since it is considered the most neutral territory within the Vatican City, with none of the Christian iconography that might be seen as offensive to the other two faiths.
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