A rift between Europe and the U.S. is hindering efforts to cut emissions of greenhouse gases under the Kyoto Protocol, said Michael Zammit Cutajar, the top U.N. climate official, as international climate change talks began yesterday in Bonn, Germany. Europe wants limits placed on emissions trading, while the U.S. wants to make wide use of such trading to meet its treaty obligations — for example, gaining credit for emissions reductions by helping developing nations build cleaner energy systems. Under the Kyoto treaty, developed nations have until the end of next year to decide how they will meet the target of cutting greenhouse gas emissions by an average of 5.2 percent from 1990 levels between 2008 and 2012. Although 83 countries and the European Commission have signed the treaty, only nine have formally ratified it; the document will become legally binding when ratified by 55 countries representing 55 percent of emissions of major world economies.