The 78-year-old Argentine pontiff also prayed at the memorial to those killed in the Sept. 11, 2001, attacks in perhaps the most solemn moment of his first visit to the United States.
He later was greeted by adoring crowds estimated at about 80,000 people as he drove in his "popemobile" through sprawling Central Park before heading to the famed Madison Square Garden sports arena for an evening Mass before about 20,000 people.
Addressing dozens of world leaders at the UN General Assembly, the spiritual head of 1.2 billion Roman Catholics railed against the "grave offense" of economic and social exclusion.
"A selfish and boundless thirst for power and material prosperity leads both to the misuse of available natural resources and to the exclusion of the weak and disadvantaged," he said.
The first pope from Latin America, Francis has often criticized unbridled capitalism in the two years of his papacy.
On September 25, he had a high-powered audience at the United Nations, which is celebrating its 70th anniversary. This year's General Assembly is believed to have attracted the highest number of leaders in UN history.
The pontiff urged government leaders to ensure their people enjoy the minimum material needs. "In practical terms, this absolute minimum has three names: lodging, labor and land," Francis said to applause.
He said humanity's future is in danger.
"The ecological crisis and the large-scale destruction of biodiversity can threaten the very existence of the human species," said Francis, who this year published the first papal encyclical, a letter to the church, dedicated to the environment.
Francis underscored an "urgent need to work for a world free of nuclear weapons" and praised the July agreement reached by the United States and other world powers to curb Iran's nuclear program as "proof of the potential of political good will and of law, exercised with sincerity, patience and constancy."
The pope also said international financial agencies should work toward "the sustainable development of countries and should ensure that they are not subjected to oppressive lending systems" that cause greater poverty, exclusion and dependence.
Francis wraps up his six-day US trip in Philadelphia on September 26 and September 27 with a Catholic summit of families, a visit to a jail and a large outdoor Mass.