Ukraine neared a final showdown with pro-Russia rebels, after Kiev forced insurgents to retreat to the last major cities they control and Moscow showed no signs of intervening to help them.

On Sunday, Ukraine said it plans to lay siege to Donetsk, a regional capital of one million residents that is the political and economic center of eastern Ukraine, and pursue rebels who fled there from Slovyansk, which had been the base of rebel military resistance in the region until government forces recaptured it over the weekend.

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