Representatives from about 200 countries are attending the 18th session for the U.N. Framework Convention on Climate Change in Qatar.
China, which has the second-largest economy in the world, said it couldn't make any new commitments on curbing greenhouse gas emissions.
"In order to eradicate poverty and try to improve living standards, we need to develop," Su Wei, China's climate negotiator, was quoted by Bloomberg News as saying. "So of course the emissions will need to grow for a period of time."
EU Climate Commissioner Connie Hedegaard said the European Union couldn't do much to help developing countries meet climate objectives. The United States said it couldn't go beyond the 17 percent reduction target for emissions by 2020.
The World Bank, in a report issued before the Doha conference began, said extreme weather patterns may grow severe even if world governments meet their climate goals. A report from the World Meteorological Organization, meanwhile, said this year was the ninth-warmest on record.