The international community should support "a trustworthy, loyal and constructive path towards peace" in the region, he said in his sermon.
"This is also a good occasion to continue our constructive dialogue with the Jews... as well as with the Muslims," the pope added.
The synod has been called mainly to discuss pastoral issues linked to the dwindling Christian communities in the Middle East, but also aims to foster peace between Israel and the Palestinians and to counter Islamic extremism.
"The vital dialogue with Judaism is one of the main objectives of the synod, along with the difficult but necessary dialogue with Islam," Nikola Eterovic, the archbishop in charge of organising synods, said earlier.
He added that Arab Christian communities were "a natural bridge with Islam."
Referring to the Middle East conflict, he said: "We hope we will be able to achieve peace and that the synod marks a step forward in this direction."
Arabic will be one of the official languages at the synod, which will bring together Catholic clergymen, an Iranian ayatollah and a senior rabbi.
The Muslim and Jewish leaders will however address the synod separately and will not meet, organisers said.
The synod talks are set to get under way on Monday and the conference runs for two weeks until October 24.
"We want maximum visibility for the Catholic church in this region, which is so vital to Christian history and which has been hit by tensions, conflicts, religious and political upheaval in the past 2,000 years," Eterovic said.
He said that the "difficult conditions" faced by Christians in the region because of discrimination and violence had forced many to emigrate.
There are around 20 million Christians in the Middle East including five million Catholics in a population of around 356 million people.
A preparatory document for the synod singled out problems of violence and discrimination faced by Christians in Iraq, Egypt and Turkey.
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