LONDON — The Russia-Ukraine conflict has seen almost four years of failed peace plans, blueprints and high-level summits. A new U.S. push to end the fighting has set off the latest flurry of diplomacy, with American, European, Russian and Ukrainian officials all trying to shape the outcome of Europe's deadliest conflict since World War II.

Tilted heavily toward Russia's aims, the U.S.-backed proposal presented to Ukraine last week set off alarm bells in Kyiv and other European capitals. Ukraine and its allies offered a set of counterproposals that revamped the proposal's points. Ukrainian and European leaders expressed optimism about the talks' momentum, but awaited responses from Washington and Moscow, which will prove decisive.

“I think we're getting very close to a deal,” President Do

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