Hopes for the last day of UN climate talks Friday were raised by a US pledge to a climate finance fund, but leaders still warned of failure amid debate on sharing the burden of carbon-emissions cuts. The pledge was contingent on an ambitious overall deal being completed at the talks, however, which French President Nicolas Sarkozy warned Thursday faced a looming disaster in the wake of the divisive emissions debate. "There is less than 24 hours. If we carry on like this, it will be a failure," Sarkozy cautioned angrily from the conference podium. "Failure at Copenhagen would be catastrophic for all of us."