There is a willingness to find common ground on sustainable development but more work is needed, an official said ahead of a conference in Rio de Janeiro. The so-called Rio+20 Conference on sustainable development begins June 20 in Brazil. The theme of the conference is the promotion of a green economy and building an institutional framework for sustainable development. U.N. Secretary-General Ban Ki-moon had called on world leaders to seize the opportunity to show their commitment to \"an inspiring vision for sustainable development.\" Negotiators have wrapped up their latest round of preparatory meetings for the Brazilian conference. Rio+20 Secretary-General Sha Zukang said delegates were working to develop a draft of the outcome document for the summit. \"I sense a real dialogue -- a real willingness to find common ground,\" he said in a statement. \"This spirit is encouraging, and we must carry it to Rio.\" Ban last month called on delegates to identify ways to support a healthy environment while at the same time developing mechanisms that stimulate economies. He added that \"nobody\" expects individual countries to sacrifice their national interests but stressed some of those interests are interdependent. Planners say 20 percent of the text of the outcome document is settled. A final preparatory committee meeting is scheduled June 13 in Rio de Janeiro.