U.S. President Joe Biden will fly to Europe on Wednesday for an emergency NATO summit on Ukraine, where invading Russian troops are stalled, cities are under bombardment and the besieged port of Mariupol is in flames.
Four weeks into a war that has driven a quarter of Ukraine's 44 million people from their homes, Russia has failed to capture a single major Ukrainian city, while Western sanctions have ostracized it from the world economy.
After failing in what Western countries say was an attempt to seize Kyiv and depose the government, Russian forces have taken heavy losses, been frozen in place for at least a week on most fronts and face supply problems and fierce resistance.