UNITED NATIONS - UN Secretary-general Ban Ki- moon on Wednesday voiced his determination to make the upcoming UN Conference on Sustainable Development, also known as Rio+20, "a conference of decisive impact and ambition."

Ban made the statement while addressing a press conference here on Rio+20, to be held on June 20-22 in Rio de Janeiro, Brazil.

"We want to make Rio+20 a conference of decisive impact and ambition," Ban said. "Progress was achieved on key issues during last week's negotiations."

The secretary-general urged world leaders to show leadership so that the international community won't "miss the once-in-a- generation opportunity" at the Rio+20 conference.

More than 130 heads of state and government, along with thousands of parliamentarians, mayors, UN officials, chief executive officers and civil society leaders, will gather at Rio+ 20 to shape and adopt new policies and measures to promote prosperity, reduce poverty and advance social equity and environmental protection.

The conference will mark the 20th anniversary of the 1992 Earth Summit, also held in Rio de Janeiro, which set out the principles of sustainable development.

"Rio+20 is a once-in-a-generation opportunity to make real progress towards the sustainable economy of the future," Ban said. "It can help us to build a more equitable world -- a world of greater prosperity and inclusive, dynamic green growth for a healthy planet."

On May 29, countries kicked off the last round of negotiations on an outcome document for the Rio+20 conference.

The five-day talks were added to provide countries with an opportunity to move forward and finalize the draft outcome document.

According to a news release, the negotiations were based on a text that had been shortened and streamlined by the co-chairs of the deliberating process, Ambassador John Ashe of Antigua and Barbuda and Ambassador Kim Sook of the Republic of Korea.

A key issue in the negotiations has been the development of so- called Sustainable Development Goals -- a set of benchmarks to guide countries in achieving targeted outcomes within a specific time period, such as on universal access to sustainable energy and clean water for all, and building on the anti-poverty Millennium Development Goals (MDGs) after the 2015 deadline.

After the last round of negotiations ended last Saturday, talks will resume during the Third Preparatory Committee Meeting for the conference, slated for June 13-15 in Rio de Janeiro, UN officials said here.

"I expect the negotiators to accomplish this in the days before ministers and world leaders arrive in Rio," Ban said. "Leaders will then act to resolve all outstanding issues. Their job is to achieve renewed political commitment for sustainable development."

"We aspire to nothing less than a global movement for generational change," he said. "We need world leaders to make the issues on the table at Rio+20 their own personal priority. Nothing else will do."

"We live in a world of economic uncertainty, growing inequality and environmental decline," he said.

The secretary-general said he expects the Rio+20 conference to produce an agreement "to define a path to an inclusive green economy that will lift people from poverty and protect the global environment."

Ban also expects the conference to produce "strong, action- oriented outcomes on a wide range of cross-cutting areas" and subsequent, necessary "progress on implementation."

"I see encouraging progress on food security and sustainable agriculture, oceans, gender equality and women's empowerment, education and energy," he said.

Some "1.4 billion people live without access to modern sources of energy," he said. "Sustainable energy for all is the golden thread that links development, social inclusion and environmental protection -- including addressing the growing threat of climate change."