* Expected to address exodus of Christians from Middle East
* Will meet refugees from Syria, Iraq
* Palestinians see visit as a morale booster
* Vatican refers to "the State of Palestine"
"This is not a protocol visit," Patriarch Louis Sako, Iraq's senior Churchman, told reporters in Amman on the eve of the visit.
"This pope feels the pain of Christians and his arrival at this time as peoples of this region are going through conflict, killings and destruction is a message of common living. It's an appeal that everyone in this region should have the courage to review their positions, to get out of this suffocating crisis," he said.
The Christian population has been declining steadily across the Middle East for generations. The Arab revolts of the recent years, the civil war in Syria, and the rise of radical Islam are only accelerating the process.
In Israel and the occupied West Bank, more Palestinian Christians are looking to leave, blaming Israel for withering their economic prospects and hobbling their freedom of movement.
"We are waiting impatiently for a word of peace from the pope that will raise morale. People in the street are asking what message will the pope carry," Sako said.
It is the first visit to the region by Francis, leader of the world's 1.2 billion Roman Catholics.
After meeting King Abdullah and saying a Mass in an Amman stadium, the pontiff will meet refugees from Syria and Iraq in Bethany on the Jordan, the place where according to tradition Jesus was baptised.
On Sunday morning Francis flies by helicopter to Bethlehem, making a six-hour visit to what the Vatican's official programme calls "the State of Palestine," a terminology Israel rejects.
In 2012, the Vatican angered Israel by supporting a vote in the United Nations General Assembly to give Palestinians de facto statehood recognition. Israel argues such a move should only come through negotiations.
Palestinians see the pope's visit, and the fact that he is flying in directly from Jordan instead of going through Israel's security barrier from Jerusalem, as a major morale boost.
To underscore his conviction that all three great monotheistic faiths can live together in the region and help to tackle the political stalemate, Francis has enlisted a rabbi and an Islamic leader to be part of a travelling papal delegation for the first time.
The two - Rabbi Abraham Skorka and Omar Abboud, director of the Institute for Religious Dialogue in Buenos Aires - are friends from when Francis was cardinal in his native Argentina.
Their presence is "an extremely strong and explicit signal" about the importance of inter-religious dialogue in the region, said the Vatican spokesman, Father Federico Lombardi.
Francis, the first non-European pope in 1,300 years, flies to Israel on Sunday night for a 32-hour visit packed with 16 events.
Threats to Christians have been scrawled by suspected Jewish radicals on Church property in the Holy Land. One read: "Death to Arabs and Christians and all those who hate Israel."
"Their writings desecrate our religious symbols. They are written on walls of churches, monasteries," said Archbishop Fouad Twal, Jerusalem's top Catholic official, speaking in Amman.
"We want these perpetrators to be put to justice and we want to know who is behind these extremist groups. They sour the peaceful atmosphere we want to create for the Holy Father," he said.
Israeli security forces, fearing that radicals might carry out a major action against the Christian population or institutions, issued restraining orders against several Jewish right-wing activists for the duration of the trip.