The latest Franco-German peace initiative for Ukraine faces its biggest test Sunday, when the leaders of France, Germany, Russia and Ukraine attempt to finalize a ceasefire plan in a four-party phone call, dpa reported. German Chancellor Angela Merkel and French President Francois Hollande have been cautious about the chances of their plan for a ceasefire, which they hammered out in talks with Ukrainian President Poroshenko on Thursday and Russian President Vladimir Putin on Friday. The phone call is expected to take place around midday central European time, according to Poroshenko.