Western officials sought to lower expectations for the plan to end the war that Ukrainian President Zelensky is presenting in New York this week, saying they don’t see it ushering in a breakthrough to the conflict with Russia. The gloomy assessment of the plan underscores a deepening sense of pessimism among allied nations as the war drags into its third year. Allies also fear a weakening of support for Ukraine if former President Trump returns to office after the elections.