The United States told the United Nations Security Council on Thursday that its proposal for a ceasefire in Ukraine was "Russia's best possible outcome" and President Vladimir Putin should take the deal.

Ukraine said Thursday it was ready to hold more talks with Russia in Istanbul next week but again demanded that Moscow supply a document setting out its conditions for peace.

Moscow’s dual campaign of intensified frontline attacks and bombardment of Ukrainian cities has further reduced the prospects for an end to the fighting.