Congress could back a global treaty to cut greenhouse-gas emissions if China and India agree to proportional cuts, the chief U.S. climate-change envoy said. An agreement Sunday at the U.N. Climate Change Conference in Durban, South Africa, for major industrial and emerging economies -- including the United States, China and India -- to work toward a 2015 global treaty that would go into effect in 2020 signifies strong collective obligation to cut emissions, Special Envoy for Climate Change Todd Stern said. As long as Beijing and New Delhi agree to emissions cuts that are \"symmetrical\" to those pledged by Washington, the final treaty stands a chance of passing Congress, which previously rejected climate legislation, including the so-called Kyoto Protocol aimed at fighting global warming. \"If the agreement has those elements then we could get into the category of the \'just very hard\' rather than the \'impossible\' [for Congress to pass],\" Stern told The Wall Street Journal. The agreement, dubbed the \"Durban platform,\" was reached after marathon negotiations that stretched past dawn Sunday, two days after the conference\'s scheduled conclusion. It says nearly 200 countries agree to draft a new international emissions treaty by 2015. Its terms also call for most industrial nations bound to reduce emissions under the Kyoto treaty to extend their commitments beyond the 2012 Kyoto expiration. Many of those countries are European Union members already bound by EU law to make cuts to satisfy the Kyoto requirements. Russia, Canada and Japan signed onto the new agreement, even though they earlier vowed not to recommit to the treaty, adopted 15 years earlier -- Dec. 11, 1997 -- in Kyoto, Japan, and entered into force Feb. 16, 2005. While 191 countries have signed and ratified the protocol, the United States would not sign the Kyoto treaty because Washington did not accept its division between developed and developing countries. The Durban platform did little to address the scale of the cuts needed in emissions, and smaller nations and environmental groups said this was a huge failing. The nations and groups said the deal was not nearly sufficient to keep emissions low enough to prevent temperatures from rising more than an average of 2 degrees Celsius (3.6 degrees Fahrenheit), a threshold above which scientists argue the effects of climate change will become much more pronounced and much harder to manage. \"While governments avoided disaster in Durban, they by no means responded adequately to the mounting threat of climate change,\" Union of Concerned Scientists policy Director Alden Meyer said. \"The decisions adopted here fall well short of what is needed.\" The independent State of the World Forum, co-founded by Nobel Peace laureate and former Soviet leader Mikhail Gorbachev, said \"governments are acting as if they have the next 40 years to reduce carbon emissions by 80 percent\" when, it argued, greenhouse gases must be cut 80 percent by 2020 to stop global warming \"before natural forces spin out of any human capacity to control events.\" \"Nothing less than the fate of human civilization is at stake,\" the forum said. \"The crisis is that stark, the choice is that clear, the leadership required is that urgent.\" Government climate-change delegates said they would work out details of the 2020 deal starting next year at meetings in South Korea and Qatar. Separately, delegates agreed to establish a Green Climate Fund to guide the flow of a promised $100 billion a year in public and private financing by 2020 to assist developing countries adapt to and mitigate the effects of climate change. The sources of the money were not determined