RIO DE JANEIRO – Leaders from the developing world sharply criticized their counterparts from richer nations during talks at the Rio+20 sustainable development conference Thursday, citing what they said is the historic responsibility industrialized nations have to clean up the globe.

Delegates from developed nations, meanwhile, said that a rapidly changing economic order and the rise of nations such as China, Brazil and India means that all nations must work together in protecting the environment.

Leaders or senior officials from 193 nations descended on Rio de Janeiro for the largest conference the United Nations has organized, with upward of 50,000 participants discussing hundreds of issues meant to get the world on a sustainable path that would allow economic growth without depleting the globe’s resources.

Cuban leader Raul Castro cited a long-standing argument of developing nations: that the old powers from Europe and the United States must contribute more in funds and efforts to clean up the globe and prevent climate change, because they ate up more of the globe’s natural resources while working their way to developed-nation status.