US lawmakers were set to vote Tuesday on a US$40 billion (A$57.6 billion) aid package for Ukraine as Washington warned Russia was likely girding for a long conflict with its neighbor.
The defense, humanitarian and economic funding should pass comfortably, with the two parties having reached an agreement on the details, and it will likely move quickly through Congress.
"Time is of the essence - and we cannot afford to wait," House Speaker Nancy Pelosi said in a letter to her Democratic colleagues.
"With this aid package, America sends a resounding message to the world of our unwavering determination to stand with the courageous people of Ukraine until victory is won.
The United States warned on Tuesday that Russian President Vladimir Putin is ready for a long war in Ukraine and will not stop at the eastern Donbas region where fighting is currently raging.
Washington's bleak prediction came as Ukraine said its membership of the European Union was a question of "war and peace" for the whole continent as it faces up to Moscow.
As it battled Russian attempts to advance in the east, Kyiv hailed what it said was EU powerhouse Germany's change of stance on a Russian oil embargo and on supplying arms to Ukraine.
Violence still raged in southern Ukraine with overnight missile strikes in the port of Odesa, while officials said some 1,000 troops were trapped in the Azovstal steelworks in the devastated city of Mariupol.
Russia invaded Ukraine on 24 February but Ukrainian forces managed to push Moscow's forces back from Kyiv, and the conflict is now well into its third month.
Mr Putin gave few hints on his plans in a speech during a huge military parade in Moscow on Monday, saying only that Russian troops were defending the "Motherland" and blaming the West for the conflict.
In Washington, top US intelligence officials said the war was at a stalemate.
President Vladimir Putin appeared to be preparing for a long conflict, and a Russian victory in the Ukraine's eastern Donbas region might not end the war, Director of National Intelligence Avril Haines said.
Russian Army servicemen ride an infantry combat vehicle in the town of Popasnaya which came under control of the Lugansk People's Republic on May 8. Source: AP / TASS/Sipa USA
US intelligence also views it as increasingly likely that Mr Putin will mobilise his entire country, including ordering martial law, and is counting on his perseverance to wear down Western support for Ukraine.
'Counting the bombs'
Moscow switched its focus to the Russian-speaking Donbas region, where separatists have been fighting since 2014, after failing to take Kyiv.
Ukraine's presidency said the "epicentre of the fighting has moved" to Bilogorivka in the Lugansk region, the site of a deadly Russian air strike on a school on Sunday that Ukrainian officials said killed 60 people.
Shelling also continued in Ukraine's easternmost strongholds, the sister cities of Severodonetsk and Lysychansk, it said. An AFP team saw columns of Ukrainian trucks moving away from Severodonetsk on Monday.
A woman stands outside a destroyed residential building in the town of Popasnaya. Source: AP / TASS/Sipa USA
His counterpart in Donetsk said three civilians were killed in the region on Tuesday.
Civilians were struggling to survive between the constantly shifting front lines.
"I feel total apathy. I am morally starved, not to mention physically," said bricklayer Artyom Cherukha, 41, as he collected water trickling from a natural spring in Lysychansk.
He was trying to get supplies for his family of nine, as people in the area steadily lose access to water and food.
"We sit here counting the bombs," Mr Cherukha said.
Russia's defence ministry said it hit 74 targets on Tuesday and downed a Ukrainian drone above the strategic Snake Island in the Black Sea.
In the south, a series of missile strikes in Odesa overnight meanwhile destroyed buildings, set ablaze a shopping centre and killed one person, just hours after a visit by European Council President Charles Michel.
Germany 'changed position'
Ukraine has been pushing Western countries for more support, and has been particularly critical of Germany for its slow response and unwillingness to give up Russian energy.
But the tone changed on Tuesday when German Foreign Minister Annalena Baerbock's surprise visit to Bucha, a town outside Kyiv where Russian troops have been accused of war crimes.
"I would like to thank Germany for changing its position on a number of issues. including arms supplies to Kyiv and supporting a Russian oil embargo", Ukrainian Foreign Minister Dmytro Kuleba told a press conference in Kyiv with Baerbock.
Mr Kuleba pushed for the European Union to admit his country, after French President Emmanuel Macron said it could take decades for Ukraine to join.
"Ukraine's membership in the EU is a matter of war and peace in Europe," said Mr Kuleba.
"One of the reasons that this war started is that Putin was convinced that Europe doesn't need Ukraine."
Destroyed Russian military vehicles lie in a garbage dump in Bucha, on the outskirts of Kyiv, Ukraine. Source: AP / Efrem Lukatsky/AP
US politicians were set to begin debate on Tuesday on a nearly $40 billion aid package, which is expected to pass comfortably with rare bipartisan support.
'Urgent evacuation'
Moscow has made more progress in southern Ukraine but "more than a thousand" Ukrainian soldiers remain in Mariupol's Azovstal steelworks, Deputy Prime Minister Iryna Vereshchuk told AFP.
The plant is the final bastion of Ukrainian resistance in the city, which has seen relentless destruction since the invasion.
An online petition calling on the United Nations to extract all remaining soldiers garnered more than one million signatures.
"Hundreds are injured. There are people with serious injuries who require urgent evacuation. The situation is deteriorating every day," said Mr Vereshchuk.
Many civilians have been evacuated from the plant in recent days, as Russia pushes for full control of Mariupol to open up a land corridor from Crimea, which it seized in 2014.
An Azov Special Forces Regiment's serviceman, injured during fighting against Russian forces, inside the Azovstal steel plant in Mariupol, Ukraine. Source: AP / Dmytro 'Orest' Kozatskyi/AP
Moscow said it would not participate in Thursday's special session of the UN Human Rights Council on Ukraine, held at Kyiv's request to examine "the deteriorating human rights situation" following the invasion.
In another step forward in building pressure on Russia, EU chief Ursula von der Leyen said she made "progress" on a proposed Russian oil embargo during talks with Hungarian Prime Minister Viktor Orban.
The populist Orban, one of Putin's closest friends in Europe, had held up the bloc's attempt to phase out Russian oil - one of the most painful measures yet taken by the West - as he pointed to economic consequences in landlocked Hungary.
Western powers on Tuesday separately accused Russian authorities of carrying out a cyberattack against a satellite network an hour before the invasion of Ukraine to pave the way for its assault.
