As preparations kicked off?Tuesday for a global summit to review progress since the historic United Nations environment conference held in Rio de Janeiro nearly 20 years ago, a senior official stressed the need for greater efforts to achieve sustainable development, UN officials said.

At the 1992 UN Conference on Environment and Development (UNCED) , also known as the Earth Summit, countries adopted Agenda 21 -- the blueprint to manage and protect the ecosystem and bring about a more prosperous future for all.

Noting that challenges remain in achieving the goals of the three pillars of sustainable development, namely economic growth, social development and environmental protection, UN Under- Secretary-General for Economic and Social Affairs Sha Zukang said "Rio+20" is one of the most important conferences on the UN agenda.

"The sad truth is that, despite two centuries of spectacular growth on our planet, we have failed to eradicate the scourge of poverty," he told delegates as they began the three-day preparatory conference for the 2012 review meeting to be held in Brazil.

"If we continue on our current path we will bequeath material and environmental poverty, not prosperity, to our children and grandchildren," he said.

The international community needed to "reinvigorate support here and now," he said, stressing the need to prevent negotiations from turning into "turf battles."

"Enough is enough," he declared, calling for States to work in an open and transparent manner as they seek to produce a meaningful outcome document for the 2012 conference.

The focus of "Rio+20" will be on a green economy in the context of sustainable development and poverty eradication, according to a news release issued by the UN, which adds that the preparations are taking place in a difficult context.

The world is facing unprecedented multi-faceted crises, including climate change, food insecurity, financial and economic uncertainty, unemployment, unsustainable consumption patterns, and disappearing species, among others.

"Our stopgap solutions in response to these crises, with short- term timeframes and sector-based approaches, can no longer suffice in tackling the multiple crises," Sha said. "Only sustainable development, with its inherent emphasis on inter-linkages to address social, economic and environmental challenges in a balanced and integrated manner, can provide long-term and durable solutions to the crises."