BONN, Germany - UN climate talks hit 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 talks, the session in Bonn bogged down with disputes about 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 such as China and India do not get off too easy. China is now the world’s top polluter.