UN World Food Program chief Ertharin Cousin arrived here Sunday to attend a United Nations summit on sustainable development and discuss plans to fight world hunger with governments and the private sector.

"WFP believes that there can be no sustainable development when so many people have been left on the sidelines of mainstream development, and WFP's attendance aims to ensure that the voices of the most vulnerable populations are heard," the organization said in a statement.

It said Cousin plans to tour Rio's Rocinha favela (slum) on Monday and speak the following day at an event on food security.

World leaders are due to debate prospects for a greener world committed to poverty eradication and environmental protection at the UN Rio+20 summit, which runs from Wednesday to Friday.