European negotiators are trying to shift responsibility onto Moscow and United States actors are seeking to corner Volodymyr Zelensky, following Ukrainian forces' recapture of Kupiansk aided by a mysterious drone-jamming system that broke Russia's siege of parts of Donbass.Analysts warn that the diplomatic manoeuvring between European and American mediators and the battlefield use of new electronic countermeasures make a lasting ceasefire unlikely despite Kyiv's local gains.