Senior NATO and Russian officials were meeting Wednesday to try to bridge seemingly irreconcilable differences over the future of Ukraine, amid deep skepticism that Russian President Vladimir Putin’s security proposals for easing tensions are genuine.

The talks comes during a week of high-stakes diplomacy and a U.S.-led effort to prevent preparations for what Washington believes could be a Russian invasion of Ukraine. Moscow denies it is planning an attack. Still, its history of military action in Ukraine and Georgia worries NATO.