Pope Francis plunged Sunday into Mideast politics during his Holy Land pilgrimage, calling the current stalemate in peace efforts "unacceptable" and winning the acceptance from the Israeli and Palestinian presidents to pay a symbolic visit to the Vatican next month to pray for peace.

Francis issued the surprise, joint invitation after landing in Bethlehem, the cradle of Christianity, in a symbolic nod to Palestinian aspirations for their own state. In another unscripted moment, he prayed at the Israeli separation barrier surrounding the biblical West Bank town and briefly donned the checkered black and white headscarf that is a symbol of the Palestinian cause.

Jubilant Palestinians cheered Francis as he arrived in Bethlehem's Manger Square, shouting "Viva al-Baba!" or "Long live the pope!" Giant Palestinian flags in red, white, green and black and the Vatican's yellow-and-white flags decorated the square, which is home to the Church of the Nativity, built over Jesus' traditional birth grotto.

At the end of Mass in the square, Francis invited Palestinian President Mahmoud Abbas and Israeli President Shimon Peres to pray with him for peace, saying: "I offer my home in the Vatican as a place for this encounter of prayer."

The offices of the Israeli and Palestinian presidents quickly confirmed that they had accepted the invitation, with the Palestinians saying the meeting would take place in June.

The invitation -- and the acceptances -- were unexpected given Francis' insistence that his three-day visit was "strictly religious" pilgrimage to commemorate a Catholic-Orthodox anniversary. But it showed that the pope, who is named after the peace-loving St. Francis of Assisi, has been able to channel his immense popular appeal to be a moral force for peace, even though the proposed meeting will be largely a symbolic affair.

Israeli-Palestinian peace talks broke down in late April, and there have been no public high-level meetings for a year.

Peres, a 90-year-old Nobel Peace laureate, is set to step down over the summer, and the meeting would take place shortly before he leaves office.

Peres, whose job is largely ceremonial, has no authority to negotiate peace, and the meeting will be merely symbolic. But he nonetheless risks upsetting Prime Minister Benjamin Netanyahu with the move.

Netanyahu has expressed anger with politicians that have reached out to Abbas at a time when the Palestinian leader is reconciling with the Islamic militant group Hamas. Israel considers Hamas a terrorist group. There was no immediate comment from Netanyahu's office.

Francis started out the second day of his three-day Mideast trip with a deeply symbolic decision to land in at a Bethlehem helipad, arriving from Jordan aboard a Jordanian helicopter. Previous popes have always come to the West Bank after first arriving in Tel Aviv, Israel.

Palestinian officials hailed Francis' decision to arrive first in Bethlehem, and to refer to the "state of Palestine." In its official program, the Vatican referred to Abbas as the president of the "state of Palestine," and his Bethlehem office as the "presidential palace."

"It's a blessed day," said Samar Sakkakini, 52, a Palestinian-American from Canton, Michigan, who attended the Mass in Manger Square. "Coming to Bethlehem and flying to Bethlehem from Jordan shows solidarity with the Palestinian people, which is wonderful. We need that."

In November 2012, the United Nations General Assembly overwhelmingly recognized a "state of Palestine" in the West Bank, Gaza and east Jerusalem -- lands Israel captured in the 1967 war -- as a non-member observer. The recognition still has little meaning on the ground, with Israel remaining in full control of east Jerusalem, which it annexed in 1967, and the West Bank.

Israel objects to the Palestinian campaign, saying it is an attempt to bypass negotiations.

Standing alongside Abbas at a welcome ceremony, Francis declared: "The time has come to put an end to this situation which has become increasingly unacceptable."

He said both sides needed to make sacrifices to create two states, with internationally recognized borders, based on mutual security and rights for everyone.

"The time has come for everyone to find the courage to be generous and creative in the service of the common good," he said, urging both sides to refrain from any actions that would derail peace.

In his remarks, Abbas voiced his concerns about the recent breakdown in U.S.-backed peace efforts and lamented the difficult conditions facing the Palestinians. He also expressed hope for peace.

"Your visit is loaded with symbolic meaning as a defender of the poor and the marginalized," he said.

Abbas listed a series of complaints against Israel, including continued settlement construction, the plight of thousands of Palestinian prisoners, Israel's control of east Jerusalem -- the Palestinians' would-be capital -- and Israel's construction of the "ugly wall" that encircles Bethlehem.

"We welcome any initiative from you to make peace a reality in the Holy Land," Abbas said. "I am addressing our neighbors -- the Israelis. We are looking for the same thing that you are looking for, which is safety, security and stability."

Security was lax by papal standards, even for a pope who has shunned the armored popemobile that his predecessors used on foreign trips.

Only two bodyguards stood on the back of Francis' vehicle keeping watch as Palestinian police kept the crowd at bay. Francis waved and warmly smiled as his car made its way through the crowd in Manger Square, at one point holding a child passed up to him.

In addition to the Israeli-Palestinian conflict, Francis also sought to encourage Palestinian Christians, whose numbers have dwindled as the conflict drags on.

Currently, Christians are roughly 2 percent of the population of the Holy Land, down from about 10 percent at the time of Israel's establishment in 1948. In Bethlehem, they are less than one third of the population.

Francis acknowledged the Palestinian Christian hardship and in his homily sought to encourage the younger generations with a strong plea for children around the globe to be protected and defended from war, poverty, disease and exile as refugees.

"All too many children continue to be exploited, maltreated, enslaved, prey to violence and illicit trafficking," he said, a mural depicting the Nativity scene with the baby Jesus wrapped in the black-and-white checkered Palestinian headdress behind him. "Today in acknowledging this, we feel shame before God."

After Mass, Francis had lunch with Palestinian families and visited a Palestinian refugee camp before flying by helicopter to Tel Aviv's Ben-Gurion airport for the Israeli leg of his trip.