Pope Francis heads to the United Nations on Friday to deliver an appeal to world leaders to help the poor, combat climate change and end conflicts that have sent desperate refugees fleeing to Europe.
Making his first address to the UN General Assembly, Francis will set the tone for an anti-poverty summit where leaders will adopt ambitious new global development goals for the next 15 years.
The Vatican flag will be raised at UN headquarters for the first time to mark the occasion, only the fifth visit by a pope to the world body in its 70-year history.
The leader of the world's one billion Catholics takes the podium at the 193-nation assembly as the United Nations stumbles in its efforts to end the war in Syria, now in its fifth year.
More than four million Syrians have been driven from their homes in what the United Nations describes as the biggest refugee crisis in a generation.
Fresh from his Washington visit with President Barack Obama and members of Congress, the pope will seek to shore up UN efforts to reach a landmark deal on tackling global warming at a Paris climate change conference scheduled for December.
The Argentine pope will address the UN assembly in his native Spanish and will focus mostly on poverty and climate, Archbishop Bernardito Auza, the Vatican's UN ambassador said.
Francis will speak "above all as a pastor, as a religious leader, as a prophet and as a father," said the ambassador, who will be hosting the pope at his Upper East Side townhouse during the New York leg of his visit.
World leaders on Friday will be adopting the UN's 17 new goals aimed at ending extreme poverty, improving health and education, combating climate change and fostering peaceful societies.
"These are also the priorities of the Catholic Church and they are at the core of the summit," said Auza.
The pontiff has made the plight of society's weakest, including the hundreds of thousands of migrants arriving in Europe, a dominant theme of his papacy.
On the turmoil in the Middle East, Francis has called for an end to the "genocide" of Christians, using a term that sets off alarm bells at the United Nations.
As Europe grapples with its worst refugee crisis since World War II, Francis has decided to lead by example, taking in a refugee family from Damascus.
He has called on "every parish, every religious community, every monastery, every sanctuary in Europe" to open their doors to the refugees and show solidarity.
The outspoken pope will meet with Secretary-General Ban Ki-moon, who will welcome him along with a group of children before he is whisked away in a golf cart through the UN's long corridors to meet with UN employees.
The select group of UN staffers won a lottery to have the chance to sit down with the 78-year-old pontiff.
Security, already tight at UN headquarters as some 160 leaders arrive for the gathering, has been stepped up for the pope's visit.
His UN address follows a rapturous welcome Thursday in New York, when adoring crowds cheered Francis as he glided down Fifth Avenue in his popemobile before he led evening prayers for dignitaries and members of the clergy at St Patrick's Cathedral.
After his UN visit, the pope goes to Ground Zero to lead an inter-faith service at the memorial to the victims of the September 11, 2001 attacks before visiting a school in Harlem.
He then rides a motorcade through Central Park to greet New Yorkers.
Some 80,000 of them have won tickets in a lottery for spots along the route he will travel.
The pope caps off his visit to New York by holding mass services at Madison Square Garden. On Saturday, he travels to Philadelphia.