"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 in a speech to the U.N. General Assembly in New York.

The spiritual leader of the world's 1.2 billion Catholics condemned the "grave offense" of economic and social exclusion.

"The dramatic reality this whole situation of exclusion and inequality, with its evident effects, has led me, in union with the entire Christian people and many others, to take stock of my grave responsibility in this regard and to speak out," he said.

On Friday, he had a high-powered audience at the United Nations, which is celebrating its 70th anniversary. The gathering for the General Assembly this year is believed to have attracted the highest number of leaders in the world body's history.

The pope called on government leaders to fight human trafficking, boost education for girls and end the destruction of biodiversity which he warned is threatening the "very existence of the human species."

He arrived in New York on Thursday night from Washington after urging the U.S. Congress to help heal many of America's divisions such as the heated political debate over immigration.

The Argentine pontiff has caught the attention of well wishers on his six-day trip to the United States by using a tiny Fiat car to get around Washington and New York, in a gesture of modesty