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President Vladimir Putin said on Saturday that Western sanctions on Russia were akin to a declaration of war and warned that any attempt to impose a no-fly zone in Ukraine would be tantamount to entering the conflict.
Moscow and Kyiv traded blame over the failure of plans to impose a brief ceasefire and enable civilians to evacuate two cities besieged by Russian forces. Russia's invasion has already driven nearly 1.5 million refugees westwards into the European Union.
Ukraine's President Volodymyr Zelenskiy made a "desperate plea" for eastern Europe to provide Russian-made aircraft to his country during a call with US senators on Saturday, said the chamber's majority leader, Chuck Schumer.
NATO, which Ukraine wants to join, has resisted Zelenskiy's appeals to impose a no-fly zone over his country, saying this would escalate the conflict outside Ukraine. But there is strong bipartisan support in the U.S. Congress for providing $10 billion in emergency military and humanitarian aid to Ukraine.
Putin said he wanted a neutral Ukraine that had been "demilitarised" and "denazified", adding: "These sanctions that are being imposed are akin to a declaration of war but thank God it has not come to that."
Putin met Israeli Prime Minister Naftali Bennett in the Kremlin to discuss the crisis, Bennett's spokesperson said. Israel has offered to mediate in the conflict, though officials have played down expectations for a breakthrough.
Ukrainian negotiators said a third round of talks with Russia on a ceasefire would go ahead on Monday. Two previous rounds have been unsuccessful and Zelenskiy has said Russia must first stop bombing.
Since President Vladimir Putin's army invaded on February 24, Russia has pummelled Ukrainian cities, killed hundreds of civilians and assaulted Europe's largest atomic power plant.
The invasion has drawn condemnation and severe sanctions from Western nations balancing punishment of the Kremlin with fears of a hazardous escalation. Moscow has seized two key cities in its 10-day-long invasion, Berdiansk and Kherson on Ukraine's southern Black Sea coast.
A United Nations monitoring mission said at least 351 civilians had been confirmed killed and 707 injured in Ukraine so far since the start of the invasion on Feb. 24, adding that the real figures were likely to be "considerably higher".
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