Mr Putin has demanded legally binding security guarantees that NATO will not expand further east or place its weapons close to Russian territory; Washington has repeatedly said no country can veto Ukraine's NATO hopes.
普京要求有法律约束力的安全保证，北约不会进一步向东扩张，也不会在俄罗斯领土附近部署武器；华盛顿一再表示，任何国家对乌克兰加入北约都没有否决权。