Lviv/Kyiv: Joe Biden flies to Europe on Wednesday for an emergency NATO summit, the US president's first trip abroad since Russia invaded Ukraine, an offensive now stalled with Ukrainian cities under bombardment and the besieged port of Mariupol 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 ostracised it from the world economy.
Russian forces have taken heavy losses and are stalled for at least a week on most fronts by supply problems and fierce Ukrainian resistance, failing in what Western countries say was an attempt to seize Kyiv and swiftly depose the government. Moscow says its "special military operation" to disarm its neighbour is going to plan.
It denies targeting civilians but has turned to siege tactics and bombardment of cities, causing massive destruction and many civilians deaths.
Worst hit has been Mariupol, a southern port completely surrounded by Russian forces, where hundreds of thousands of people have been sheltering since the war's early days, under constant bombardment and with no access to food, water or heat.
New satellite photographs from commercial firm Maxar released overnight showed massive destruction of what was once a city of 400,000 people, with columns of smoke rising from residential apartment buildings in flames.
No journalists have been able to report from inside the Ukrainian-held parts of the city for more than a week, during which time Ukrainian officials say Russia has bombed a theatre and an art school used as bomb shelters, burying hundreds of people alive. Russia denies targeting those buildings.
Biden, due to arrive on Wednesday evening, will meet NATO and European leaders in an emergency summit at the Western military alliance's Brussels headquarters. The leaders are expected to roll out additional sanctions against Russia on Thursday. Sources said the US package would include measures targeting Russian members of parliament.
Biden will also visit Poland, which has taken in most of the more than 3.5 million refugees who have fled Ukraine and served as the main route for Western supplies of weapons to Ukraine.
Kyiv hopes that Russia's President Vladimir Putin, having failed to swiftly subdue what he describes as an illegitimate nation, can now be compelled to negotiate a ceasefire and withdrawal. Peace talks have been ongoing since last week.
"It's very difficult, sometimes confrontational," President Volodymyr Zelenskiy said in an overnight address. "But step by step we are moving forward."
But despite its losses so far, Russia may still be hoping to make more gains on the battlefield, especially in the east, in territory including Mariupol which Moscow demands Ukraine cede to Russian-backed separatists.
In a daily intelligence update, Britain's defence ministry said the entire battlefield across northern Ukraine - which includes huge armoured columns that once bore down on Kyiv - was now "static", with invaders apparently trying to reorganise.
But in the east, the Russians were trying to link troops at Mariupol with those near Kharkiv in the hope of encircling Ukrainian forces, while in the southwest they were bypassing the city of Mykolayiv to try to advance on Odesa, Ukraine's biggest port.
Ukrainian officials described sporadic shelling in other cities overnight, with two civilians killed in the Mykolayiv region, a bridge destroyed in the Chernihiv region, and residential buildings and a shopping mall struck in two districts of Kyiv, wounding at least four people.