A debate over climate aid is widening the rift between richer and poorer nations at United Nations climate talks in Warsaw, creating another obstacle in the fight against global warming.

Industrial nations have pledged to boost aid to $100 billion a year by 2020 for developing countries seeking to reduce their own pollution and cope with more intense storms and higher sea levels that come with higher temperatures. Poorer countries are seeking a predictable funding schedule to help them plan, and the richer states aren’t providing that.