Meanwhile, Russia appeared close to capturing a key city in the Donetsk region on Tuesday, complicating the situation further.

European leaders will hold a videoconference on Wednesday ahead of one with U.S. President Donald Trump to coordinate negotiations to end the war in Ukraine with Russia's President Vladimir Putin, a German government spokesperson said on Monday.

Zelenskyy suggests he could be ready to make 'painful but acceptable' territorial concessions – but that still might not be enough for Russia