U.N. climate talks ran into gridlock Thursday as a widening rift between rich and poor countries risked undoing some advances made last year in the decades-long effort to control carbon emissions that scientists say are overheating the planet.

As so often in the slow-moving negotiations, the session in Bonn bogged down with disputes over technicalities. But at the heart of the discord was the larger issue of how to divide the burden of emissions cuts between developed and developing nations. Developing nations say the industrialized world - responsible for most of the emissions historically - should bear the brunt of the emissions cuts while developed nations want to make sure that fast-growing economies like China and India don't get off too easy. China is now the world's top polluter.

"There is a total stalemate," said Artur Runge-Metzger, the chief negotiator for the European Union.

The negotiations in Bonn were meant to build on a deal struck in December in Durban, South Africa, to create a new global climate pact by 2015 that would make both rich and poor nations rein in emissions caused by the burning of oil and other fossil fuels. But on the next-to-last day of two weeks of talks there was little sign of progress, as different interpretations emerged on what, exactly, was agreed upon last year.

"There is distrust and there is frustration in the atmosphere," Seyni Nafo, spokesman for a group of African countries, told The Associated Press.

The European Union claims China and other developing countries are backsliding on commitments made in Durban to bring the discussion on emissions cuts from both rich and poor nations into one forum, instead of the current structure, which has two parallel negotiation tracks. Developing countries - backed by climate activists - accuse the U.S., EU and other industrialized nations of trying to evade commitments made in previous negotiations and shift responsibilities for tackling climate change to the developing world.

"Developed countries like the U.S., Japan, Canada and Russia ... have consistently blocked references to the existing legal principles, while continuing to ignore the fact that their meager emission cut targets expose the world's most vulnerable people to climate change's devastating effects," said Mohamed Adow, a senior climate change adviser at Christian Aid.

Meanwhile, emissions are going up, not down.

The Paris-based International Energy Agency said Thursday that carbon emissions from fossil fuels reached a record high of 31.6 gigatons in 2011, a 3.2 percent increase from the year before.

Despite improving on its energy efficiency, China accounted for the biggest contribution to the global increase, with emissions growing by 720 million tons, or 9.3 percent, the IEA said.

U.S. emissions fell by 1.7 percent, "primarily due to ongoing switching from coal to natural gas in power generation and an exceptionally mild winter," the agency said, while Japan's emissions rose 2.4 percent as it increased the use of fossil fuels in the wake of the Fukushima nuclear disaster.

The IEA data also showed that India moved ahead of Russia to become the fourth largest CO2 emitter, behind China, the U.S. and the EU.

Since their launch in the early 1990s, the U.N. talks have had little success reducing emissions of the heat-trapping gases that a large majority of climate scientists say are warming the Earth, with potentially devastating consequences for poor countries ill-prepared to deal rising sea levels, floods, droughts and other effects of a changing climate.

Actions taken and pledged so far fall well short of what the U.N. experts say is needed to achieve the goal of preventing global temperatures from rising more than 2 degrees Fahrenheit (1.2 degrees Celsius) above current levels by the end of this century.

The only existing binding treaty, the 1997 Kyoto Protocol, was shunned by the U.S. because it doesn't impose any emissions targets on China, thus leaving out the two biggest carbon emitters on the globe. It was set to expire this year but countries agreed in Durban to extend it, though they haven't agreed on how long. Canada, Japan and Russia have refused to make any new commitments under Kyoto, meaning it only covers about 15 percent of global emissions.