President Petro Poroshenko attends Auschwitz ceremonies Tuesday. ENLARGE Photo: Getty Images Ukrainian troops beat back fresh attacks by pro-Russia militants on a crucial rail hub Tuesday, part of recent heavy fighting that is sapping the Ukrainian administration of options and finances as it works to fend off a wider Russian-supported onslaught. U.S. and European leaders threatened new sanctions in the wake of a rebel rocket attack that killed dozens of Ukrainian civilians over the weekend, but Russian President Vladimir Putin appeared ready to shrug off any new measures. On Tuesday, he continued to blame Kiev for the fighting and for “gunning down civilians in cold blood.” The Kremlin denies giving support to pro-Russia rebels in eastern Ukraine or sending Russian troops, which Kiev said on Tuesday numbered as many as 15,000. Kiev and Western officials say a fresh infusion of Russian armor in the past two weeks has been […]