Negotiations on a new global charter to protect the environment and eradicate poverty were heading into overtime on Friday as officials admitted they faced a battle to seal a deal ahead of next week\'s UN summit. The cornerstone document of the June 20-22 \"Rio+20\" summit aims at setting a path for nurturing the planet\'s natural bounty and promoting green growth. But after five months of wrangling, talks on the draft entered their final scheduled day on Friday with agreement on only 28 percent of the 81-page text, they said. Responsibility for steering the haggle was expected to be handed on Saturday to Brazil, the conference host, said Nikhil Seth of the UN\'s Division for Sustainable Development. \"It\'s everyone\'s hope that by (June) 19 at the latest, everything will be wrapped up,\" he said. Seth added: \"There is a sense of optimism, but in every room there is a sense also that the enemy now is time.\" Brazilian delegation chief Luiz Alberto Figueiredo said: \"We have no intention to hand undecided issues to heads of state. We intend to wrap up negotiations by the 19th.\" The Conference on Sustainable Development is the 20-year followup to the Earth Summit where UN members made historic agreements to combat climate change, wildlife loss and desertification. An expected turnout of 116 heads of state or government will cap a week-long gathering of as many as 50,000 activists, business executives and policymakers. Progress on the so-called outcome document has been mired by discord, often pitching developing economies against rich ones. \"There are lively discussions still going on,\" the US special envoy for climate change, Todd Stern, said in a conference call with journalists. \"There\'s still a lot to be wrestled with.\" Problems include a set of \"Sustainable Development Goals\" to succeed the UN\'s Millennium Development Goals, due to expire in 2015, how to encourage the green economy and mustering funds to promote sustainable development. Poorer countries are calling for 30 billion dollars a year. But another area of friction is over how or whether to reaffirm the \"Rio Principles\" set down in the 1992 summit, which say countries have \"common but differentiated responsibilities.\" The phrase is designed to ensure that poor countries do not have to shoulder the same burden as rich countries in fixing Earth\'s environmental problems. But Stern was scathing, saying the phrase belonged to an era when China and other countries that today are emerging giant economies were far poorer and less able to contribute. \"The idea, the phrase, (if) taken to mean a firewall between developed and developing countries, is completely unacceptable to us,\" he said. The summit is taking place against a backdrop of ever-worsening news on the environment and financial or fiscal crises in rich economies have slashed the political will for concessions. \"We have essentially lost 20 years from the Rio Earth Summit in 1992. This is of first-order importance, yet the world -- and especially the political system -- does not reflect that importance,\" Jeffrey Sachs, director of the Earth Institute at Columbia University in New York, said in an interview for AFP Blogs (blogs.afp.com/geopolitics). A colorful counter-conference got under away at a Rio park, with the dramatic appearance of 82-year-old Amazonian chief Raoni, stomping and brandishing a club. The \"People\'s Summit\" will feature several different demonstrations, including a main march expected to draw 50,000 people on June 20, when the official Rio+20 gets underway.