Pope Francis on Sunday told the Israeli and Palestinian presidents that they "must respond" to their people's yearning for peace in the Middle East and find "the strength to persevere undaunted in dialogue."

The pope made his appeal to Shimon Peres and Mahmoud Abbas at the end of an unprecedented prayer meeting among Jews, Christians and Muslims in the Vatican gardens that marked the first time the two presidents have met in public in more than a year.

"Peacemaking calls for courage, much more so than warfare. It calls for the courage to say yes to encounter and no to conflict: yes to dialogue and no to violence; yes to negotiations and no to hostilities; yes to respect for agreements and no to acts of provocation; yes to sincerity and no to duplicity. All of this takes courage, it takes strength and tenacity," the pope said.

Francis said seeking peace was "an act of supreme responsibility before our consciences and before our peoples" and noted that millions around the world of all faiths were praying together with them for peace.

"We have heard a summons, and we must respond. It is the summons to break the spiral of hatred and violence, and to break it by one word alone: the word 'brother'," he said.

He said the children who have been the innocent victims of wars and conflicts made the search for peace an imperative.

"The memory of these children instils in us the courage of peace, the strength to persevere undaunted in dialogue, the patience to weave, day by day, an ever more robust fabric of respectful and peaceful coexistence, for the glory of God and the good of all," he said.

Earlier on Sunday, Peres and Abbas embraced in the foyer of the Vatican hotel where Francis lives, joked together and shared a minibus with Francis and the spiritual leader of the world's Orthodox Christians for the quick trip across the Vatican to the garden ceremony.

There on the lawn, Francis sat between the two presidents, with the Israeli and Palestinian delegations and Vatican cardinals flanking them, as a string ensemble played.

Vatican officials have insisted that Francis has no political agenda by inviting the two leaders to pray at his home other than to rekindle a desire for peace between the two parties. But the meeting could have significance beyond mere symbolism.

"In the Middle East, symbolic gestures and incremental steps are important," noted the Rev. Thomas Reese, a veteran Vatican analyst for the National Catholic Reporter. "And who knows what conversations can occur behind closed doors in the Vatican."

The prayers focus on three themes common to each of the religions: thanking God for creation, seeking forgiveness for past wrongdoing and praying to God to bring peace to the region.

Vatican officials have described the prayer evening as something of a "time-out" in political negotiations, merely designed to rekindle the desire for peace through prayers common to all the main faith traditions in the Holy Land.

But even Francis' secretary of state, Cardinal Pietro Parolin, has said the power of prayer shouldn't be discounted for its ability to change reality.

"Prayer has a political strength that we maybe don't even realize and should be exploited to the full," he said at the end of Francis' Mideast trip. "Prayer has the ability to transform hearts and thus to transform history."

Peres, who has no formal role in peace negotiations, holds a largely ceremonial post and leaves office at the end of the month.

Nadav Tamir, a political adviser to Peres, said Sunday the Israeli government authorized the trip and Israeli Prime Minister Benjamin Netanyahu was in "constant contact" with Peres. Speaking on Israeli Army Radio, Tamir stressed the meeting was not political, even though he said Peres and Abbas were expected to discuss political developments when they meet in private after the prayer.

Netanyahu had urged the world to shun Abbas' new unity government which took office last week because it is backed by the Islamic militant group Hamas. His pleas have been ignored by the West, with both the U.S. and the European Union saying they will give the unity government a chance.

Peres' participation thus undermines Netanyahu's attempts to isolate the Palestinians and instead adds to the growing isolation of Netanyahu's hard-line position. Netanyahu's office has declined repeated requests for comment about the Vatican summit.

Peres, 90, deviated from his prepared remarks in the garden to add a personal note as his term as Israeli president comes to an end.

"I was young. Now I am old," he said. "I experienced war. I tasted peace. Never will I forget the bereaved families — parents and children — who paid the cost of war. And all my life I shall never stop to act for peace, for generations to come.

"Let's all of us join hands and make it happen," he said.

Abbas made a few political points, saying Palestinians craved peace as well as "dignified living" and "freedom in our sovereign and independent state."

"We want peace for us and for our neighbors," he said, according to his prepared text.

The two met privately for about 15 minutes inside a nearby Vatican villa.

Open gallery view Peres, Abbas and Pope Francis during a prayer service at the Vatican. Credit: Haim Tzach / GPO