Ukraine has been stockpiling arms and ammunition since before Donald Trump’s election victory last November, but over time the US president’s halting of military aid will be felt in air defence and other high-value weapons systems the US is uniquely placed to supply. “They got a lot of kit in before the inauguration,” said a senior western official, adding that it would be enough to keep Ukraine in the fight “well beyond” what they described as the period during which ceasefire negotiations were expected to last. A defence expert in Kyiv said Ukraine had a “safety margin of about six…