The impasse over aid from the U.S. and Europe has Ukraine’s allies contemplating something they’ve refused to imagine since the earliest days of Russia’s invasion: that Russian President Vladimir Putin may win.

With more than $110 billion in assistance mired in political disputes in Washington and Brussels, how long Kyiv will be able to hold back Russian forces and defend Ukraine’s cities, power plants and ports against missile attacks is increasingly in question.

Beyond the potentially catastrophic consequences for Ukraine, some European allies have begun to quietly consider the impact of a failure for NATO in the biggest conflict in Europe since World War II. They’re reassessing the risks an emboldened Russia would pose to alliance members in the east, according to people familiar with the internal conversations who asked for anonymity to discuss matters that aren’t public.