Officials from almost 200 countries are preparing for a last push at an annual U.N. summit to finalize rules for the Paris climate accord amid signs that resolving the issue of international carbon markets may be postponed for another year. Negotiators pored over revised drafts Friday, hours before the U.N. talks in Madrid were officially meant to end. Germany’s environment minister said a decision Thursday by European Union leaders in Brussels to make the bloc ” climate neutral” by 2050 would provide a boost to negotiations in the Spanish capital during the final hours.