Ukrainian President Volodymyr Zelenskyy has challenged his Russian counterpart Vladimir Putin to sign a cease-fire to end fighting as the two sides work to set up a meeting to create a last peace after more than three years of war sparked by Moscow's full-scale invasion of its neighbor.

He criticised Russia's proposals, describing them as 'ultimatum'. For any peace, Russia called for global recognition of occupied territories and Kyiv's neutrality in international affairs.

President Donald Trump is "open" to meeting his Russian and Ukrainian counterparts in Turkey, the White House said, amid a push for an elusive ceasefire.

"The military standoff needs to stop in order to stabilize the situation," Deputy Foreign Minister Sergey Ryabko said.