By Natalia Zinets KYIV (Reuters) -Ukraine said on Friday it would not yield to pressure from Moscow to negotiate with Russian-backed separatist leaders, after the latest four-nation talks ended with no breakthrough on ending eight years of fighting. Russia’s envoy to the talks said there was “zero” progress and accused Ukraine of putting forward absurd proposals. The failure marked a setback for efforts to defuse the wider Ukraine crisis in which Russia has massed more than 100,000 soldiers near Ukraine’s borders, raising fears of a war. Ukraine says 15,000 people have been killed since 2014 i…