GENEVA (Reuters) - About 45 nations met on Thursday to seek ways to raise billions of dollars in aid to help the poor combat climate change as the United Nations warned them of a long haul to slow global warming. Environment ministers and senior officials in Geneva were reviewing whether rich nations, hit by austerity cuts, are keeping a promise of $30 billion in new and additional climate aid for 2010-12 made at the UNs Copenhagen summit. The funds are critical to build trust between rich and poor, Christiana Figueres, the UNs climate chief, told Reuters in an interview. About 120 countries in Copenhagen also pledged to increase aid for developing nations to $100 billion aid a year from 2020. Figueres said cash could be a key to unlock progress on other climate problems, such as sharing clean technologies or protecting carbon-storing forests at the next meeting of environment ministers in Cancun, Mexico, from November 29-December 10. Swiss Environment Minister Moritz Leuenberger told the start of the two-day talks that the regulation of the financial issues is a key precondition for the successful conclusion of the climate negotiations in Cancun. But Figueres predicted there would be no new global treaty to combat climate change in Cancun, even though she said that extreme weather such as floods in Pakistan or Russias heat wave were warning bells about the risks of inaction. I dont think that governments are considering (a treaty) for Cancun, she said. A year ago, many nations were hoping that the Copenhagen summit in December would be a big bang deal to help solve climate change. But that didnt happen and Figueres said it was more realistic to look for gradual progress in solving climate change, adding that there was no magic bullet. Cancun could end up setting a new deadline for working out a more binding deal, perhaps by the end of 2012.