Another round of U.N. climate talks closed Friday without resolving how to share the burden of curbing man-made global warming, mainly because countries don't agree on who is rich and who is poor.

China wants to maintain a decades-old division between developed and developing countries, bearing in mind that, historically, the West has released most of the heat-trapping gases that scientists say could cause catastrophic changes in climate.

But the U.S. and Europe insisted during the two-week talks in Bonn that the system doesn't reflect current economic realities and must change as work begins on a new global climate pact set to be completed in 2015.

"The notion that a simple binary system is going to be applicable going forward is no longer one that has much relevance to the way the world currently works," U.S. chief negotiator Jonathan Pershing said.