After endless days of discussions, noisy protests, and a near-walkout by delegates from the European Union, negotiators at the World Summit on Sustainable Development reached agreement yesterday on a plan to address poverty and environmental degradation. The plan is expected to be ratified by the more than 100 world leaders assembled for the summit in Johannesburg, South Africa. It outlines initiatives on everything from removing trade barriers that harm the economies of developing nations to providing basic sanitation to poor people, to restoring marine fish stocks. Most environmentalists and some delegates were disappointed with the plan — especially with provisions on renewable energy. The E.U. had pushed for a worldwide pledge that 15 percent of all energy use would come from renewable sources by 2010. The U.S. and some oil-producing countries opposed that target, or any specific targets at all, and eventually carried the day. “We don’t seem to be making progress. We seem to be backsliding,” said Michael Strauss, a spokesperson for a coalition of environmental and activist groups.