Russian President Vladimir Putin on Friday cautiously welcomed a U.S. proposal to end Moscow's nearly four-year war in Ukraine, saying it “could form the basis of a final peace settlement”.

Putin also accused Kyiv of opposing the plan, which contains many of the Kremlin’s longstanding demands while offering limited security guarantees to Ukraine.

Ukrainian President Volodymyr Zelenskyy painted the plan as putting his country before a painful choice, between keeping the support of a key ally or standing up for its sovereignty following Russia's invasion.

But he also pledged to "work calmly" with Washington and others towards a resolution.

The plan foresees Ukraine handing over territory to Russia, something Kyiv has repeatedly ruled out, reduces the size of its army and blocks a coveted path to NATO membership.