OHANNESBURG, Sept. 2 — The first of 100 world leaders who are to address the environmental summit meeting here issued strong criticism today of rich polluting nations — the United States chief among them — for refusing to ratify a treaty intended to prevent the devastating effects of climate change.
But despite the pointed remarks from the leaders of France, Britain and other nations about the treaty, known as the Kyoto Protocol, American officials succeeded tonight in winning an important concession.
A plan for converting world energy production from fossil fuels to solar and wind power and other renewable energy sources no longer contains a commitment to ensuring that such sources account for 15 percent of world energy output by 2010.
Officials said delegates were close to final agreement on the plan, now that the provision has been dropped.
Yvon Slingenberg, a senior member of the European Union's delegation, expressed disappointment that the United States and other countries had refused to embrace the targets for renewable energy.
"We would have preferred to have a target and we would have preferred to have a timeline," Ms. Slingenberg said. "This was not possible. We tried until the very end. At a certain stage there is a point of exhaustion."
Environmentalists, too, were critical, saying the United States, which has opposed targets and timetables, had repeatedly watered down the text. "It's a shameful abrogation by governments who should be delivering on protection of climate, on protection of air quality," said Kate Hampton, international coordinator of Friends of the Earth, an advocacy group.
The United States says it prefers concrete action to target dates that might ultimately prove meaningless. In getting the time frame eliminated, it found allies in developing countries, as well as Japan and Australia.
Paula Dobriansky, under secretary of state for global affairs, defended the Bush administration's position, saying, "The document clearly highlights the need to increase access to modern energy services and signals the valuable role renewable energy will play in the future."
During the course of the meeting, the administration has acceded to other proposals, agreeing for example on efforts to halve the number of people without sanitation by 2015 and to reduce the loss of endangered plants and animals by 2010.
But the concessions have not quieted the discontent among America's allies, who argue that as the world's most powerful nation, the United States should do more to protect the environment. "Our house is burning down and we're blind to it," President Jacques Chirac of France said in his speech here today. "The earth and humankind are in danger, and we're all responsible. It's time to open our eyes."
"Climate warming is still reversible," Mr. Chirac asserted. "Heavy would be the responsibility of those who refused to fight it."
In his speech, Prime Minister Tony Blair of Britain said leaders could not afford to allow poverty and environmental degradation to continue unchecked. "Kyoto is right; it should be ratified by all of us," he said. "The consequences of inaction on these issues are not unknown. They are calculable. Poverty and environmental degradation, if unchecked, spell catastrophe for our world. That is clear."
In speechmaking today, several leaders took the opportunity to weigh in on their own specific issues concerning the environment, politics and one another.
President Hugo Chávez of Venezuela called for the creation of a global fund to ease poverty. President Yoweri Museveni of Uganda urged rich countries to open their markets to products from poor countries.
Mr. Chirac called for an international solidarity tax on items like airline tickets and health products that would create a pool of money to help developing nations.
And President Robert Mugabe of Zimbabwe received rousing applause from his fellow heads of state when he told Mr. Blair to stop interfering with his land redistribution program.
Mr. Mugabe, saying sustainable development was not possible without land reform, said: "Blair, keep your England. Let me keep my Zimbabwe."
Secretary of State Colin L. Powell, who is representing the United States in the absence of President Bush, will take his five minutes at the podium on Wednesday, officials say.
American officials dismissed the criticisms made today, saying most delegations had responded positively to American contributions to the summit meeting's action plan.
John F. Turner, assistant secretary of state for oceans and international environmental and scientific affairs, said he was pleased with the commitments that had been made. He pointed to agreements on sanitation, improved governance and a deal to restore depleted fisheries, where possible, by 2015.
As for global warming, Mr. Turner reiterated Washington's position. Mr. Bush asserted in rejecting the Kyoto treaty that it was unfair that the accord did not bind developing nations, especially China and India, that are also major emitters of gases that trap heat in the atmosphere.
"We're strong supporters of the compromise on climate change," Mr. Turner said. "We have our sovereign choice to pursue another path."