The pontiff, whose reform-minded approach has won him a rousing global following even from non-believers, offered his vision of a better world on his latest stop of a US tour that has brought thousands to the streets to welcome him.
Taking the UN rostrum, the leader of the world's more than one billion Catholics called for reform to global bodies, including the UN Security Council and financial lenders, to "limit every kind of abuse and usury."
In a wide-ranging speech, Francis touched on an array of hot-button topics, including the persecution of Christians, the Iran nuclear deal, drug trafficking -- "silently killing millions" -- and the rights of girls to an education.
"The international financial agencies should care for the sustainable development of countries and should ensure that they are not subjected to oppressive lending systems which, far from promoting progress, subject people to mechanisms which generate greater poverty, exclusion and dependence," Francis said.
Francis, the first Latin American pope, hails from Argentina -- where economic crises have fueled criticism of the conditions set by the International Monetary Fund and other institutions. Francis also gave his latest passionate plea to protect the environment, as he voiced confidence that a high-stakes UN conference on climate change would reach a "fundamental and effective" agreement in Paris in December.
Reaffirming a "right to the environment," the pontiff, 78, said that the universe was "the fruit of a loving decision by the Creator" and that humanity "is not authorized to abuse it, much less to destroy it."
"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 poor fare worst because they are "forced to live off what is discarded and suffer unjustly from the abuse of the environment," he said. Francis appealed for peace around the world and made his latest plea for the protection of Christians, as well as others, persecuted by extremists in Syria and Iraq.
The pope offered a strong endorsement of Iran's agreement with the United States and five other world powers to limit its nuclear program, a day after Francis spoke to the US Congress, where many lawmakers vehemently oppose the deal.
The Iran agreement "is proof of the potential of political goodwill, exercised with sincerity, patience and constancy," Francis said. "I express my hope that this agreement will be lasting and efficacious, and bring forth the desired fruits with the cooperation of all the parties involved," he said.