(CNN) -- As delegates ended the three-day Rio+20 summit with a 53-page statement called "The Future We Want," activists slammed the U.N. conference on sustainable development as a "failure of epic proportions."
U.N. Secretary-General Ban Ki-moon described the document as a "firm foundation for social, economic and environmental well-being."
"Rio+20 has affirmed fundamental principles -- renewed essential commitments -- and given us new direction," Ban said in a statement.
But the conservation group Greenpeace said the summit, formally known as the United Nations Conference on Sustainable Development, was "over before it started."
"One by one, the few proposed commitments and targets were deleted," Greenpeace International Executive Director Kumi Naidoo said in a statement.
"Rio+20 has been a failure of epic proportions," Naidoo added. "The only outcome of this summit is justifiable anger, an anger that we must turn into action."
Aid group Oxfam also slammed the once-in-a-decade event as a failure.
"Rio will go down as the hoax summit," Oxfam chief executive Barbara Stocking said. "We elect governments to tackle the issues that we can't tackle alone. But they are not providing the leadership the world desperately needs."
"Paralysed by inertia and in hock to vested interests, too many are unable to join up the dots and solve the connected crises of environment, equity and economy," her statement added.
Australian Prime Minister Julia Gillard defended the summit Saturday, saying she understood why many people were dissatisfied with the outcome, but stressed there had been progress.
"I do understand that there are people who will look at aspects of what has been resolved here and feel some sense that it's not enough, but we shouldn't forget where progress has been made," she said.
"I think agreeing to sustainable development goals is progress," Gillard added.
About 100 heads of state and government were among roughly 40,000 delegates who attended the meeting, which the U.N. called an "historic opportunity to define pathways to a safer, more equitable, cleaner, greener and more prosperous world for all."
It came 20 years after the Earth Summit in Rio which adopted Agenda 21, an action plan for sustainable development in the 21st century.
During the meeting, the U.N. said some $513 billion had been committed to a number of issues including energy, food security, access to drinking water and ocean management.
Pledges made during the summit include a 100-million tree planting program, plans to lift African women out of poverty through green economy businesses, and a commitment to recycle 800,000 tons of PVC each year, the United Nations said.
On Thursday, Ban launched a "Zero Hunger Challenge," an initiative backed by the U.N. Food and Agriculture Organization, the International Fund for Agricultural Development (IFAD), the World Food Programme (WFP), the U.N. Children's Fund (UNICEF), the World Bank and Bioversity International.
The U.N. described it as a "personal challenge" to everyone worldwide to work together to end hunger.
The "challenge" has five main goals, including "100%" access to adequate food all year around, ending malnutrition in pregnancy and early childhood, making all food systems sustainable, increasing productivity and income on family farms and eradicating all food waste.
The initiative earned praise from the head of Oxfam, which called it a "welcome ray of hope."