BRUSSELS — As Ukraine's Western backers slowly inch towards a "coalition of the willing" with a new UK-French-led peace plan, they still lack a strong voice to lead the effort and are reluctant to go it alone without the US.

British Prime Minister Keir Starmer has told leaders gathered Sunday for a summit on the war in Ukraine that they need to step up and continue to support Kyiv, and meet a “once in a generation moment”