Moscow’s forces are three miles from Dnipropetrovsk, a province they have never invaded. If they cross in, the advance would be a morale blow to Ukraine and complicate any territorial negotiations.

The Kremlin said on Thursday that any plan to send European troops to Ukraine as part of a potential peacekeeping mission would be unacceptable for Russia and that it was monitoring such proposals with concern.

Europeans are split on whether to send troops to Ukraine, with polls showing most citizens in the U.K, Denmark and Germany favor sending in peacekeepers, but elsewhere, the idea of troops getting sucked into the war is very unpopular.

An emergency summit held by European leaders on Monday to discuss the United States' plans to end the war in Ukraine failed to yield any immediate results, with leaders split on the issue of sending peacekeeping troops to monitor a potential ceasefire in Ukraine.