The presidents of the United States and France said they would hold Russia to account for its actions in Ukraine and the European Union reached tentative agreement on an oil price cap to squeeze Moscow's export earnings.
Joe Biden also said he would be willing to speak directly to Russian President Vladimir Putin about ending the war but that there was no sign of that happening. In March, a month into Russia's invasion, Biden called Putin a "butcher" over his actions and said the Kremlin leader "cannot stay in power".
Now, after more than nine months of fighting and with winter tightening its grip, Western countries are trying to boost aid for Ukraine as it reels from missile and drone attacks that have left millions without heating, electricity and water.
Russia accused the United States and NATO of playing a direct and dangerous role in the war and said Washington had turned Kyiv into an existential threat for Moscow which it could not ignore.
Fighting continued to rage in eastern Ukraine, with the town of Bakhmut the main target of Moscow's artillery attacks, while Russian forces in the southern Kherson and Zaporizhzhia regions were on the defensive, Ukraine's General Staff said.
In a bid to reduce the money available for Moscow's war effort, the European Union tentatively agreed on Thursday on a $60 a barrel price cap on Russian seaborne oil, according to diplomats. The measure would need to be approved by all EU governments in a written procedure by Friday.
Ukrainian President Volodymyr Zelensky, in a video posted on Thursday night, said that Dec. 1 was the anniversary of a referendum 31 years ago when Ukraine - then still part of the Soviet Union - voted overwhelmingly in favour of independence.
"Our desire to live freely ... will not be broken. Ukrainians will never again be a tiny stone in some empire," Zelensky said.
Biden and French President Emmanuel Macron said in a joint statement after Oval Office talks on Thursday that they were committed to holding Russia to account "for widely documented atrocities and war crimes, committed both by its regular armed forces and by its proxies" in Ukraine.
Biden told reporters he was prepared to speak with the Russian president "if in fact there is an interest in him deciding he's looking for a way to end the war," adding that Putin "hasn't done that yet".
Macron said he would continue to talk to Putin to "try to prevent escalation and to get some very concrete results" such as the safety of nuclear plants.
The International Atomic Energy Agency hopes to reach an agreement with Russia and Ukraine to create a protection zone at the Zaporizhzhia nuclear power plant by the end of the year, the head of the UN atomic watchdog, Rafael Grossi, told Italian newspaper La Repubblica in an interview.
Repeated shelling around the Russian-held plant has raised concern about the potential for a grave accident just 500 km (300 miles) from the site of the world's worst nuclear accident, the 1986 Chornobyl disaster.
There are no political talks under way to end the war, which Russia began on Feb. 24 as a "special military operation" claiming its aim was to disarm its neighbour and root out leaders it characterises as dangerous nationalists.
Ukraine and the West call it an imperialist land grab, which has killed tens of thousands of Ukrainian civilians and soldiers on both sides.
Ukraine's armed forces have lost somewhere between 10,000 and 13,000 soldiers so far, presidential adviser Mykhailo Podolyak told a Ukrainian television network on Thursday.
"We will never urge the Ukrainians to make a compromise which will not be acceptable for them, because they are so brave," Macron said in Washington.
Russia has recently intensified a campaign to knock out power, water and heat supplies in Ukrainian cities. Ukraine and the West say the strategy deliberately intends to harm civilians, a war crime, something Moscow denies.
Kyiv Mayor Vitaliy Klitschko on Thursday told residents to stock up on water, food and warm clothes in the event of a total blackout.
The attacks on infrastructure are likely to increase the cost to keep Ukraine's economy going next year by up to $1 billion a month, and aid to the country would need to be "front-loaded", IMF head Kristalina Georgieva told a conference on Thursday.
In the early hours of Friday, Russian forces shelled a building in the Ukrainian-held city of Zaporizhzhia, setting it ablaze, city official Anatoly Krutyev said.
Russian forces, having abandoned the strategic southern city of Kherson in November, are trying to establish defensive positions and are shelling several towns to the north, Ukraine's General Staff said in a statement overnight.
Battlefield reports could not be independently confirmed.
Russian Foreign Minister Sergei Lavrov, speaking during an annual news conference in Moscow, said NATO and the United States were participating directly in the conflict by sending lethal weapons into Ukraine "to kill Russians".
Lavrov also said recent missile strikes targeting Ukraine's civil infrastructure were aimed at preventing Kyiv from importing Western arms. He did not explain how such attacks could achieve that aim.
Germany plans to deliver seven Gepard tanks to Ukraine next spring, adding to 30 already being used to fight against Russian forces, Spiegel magazine reported on Friday.
In a sign that some channels of communication remain open, Russia's Defence Ministry and the head of Ukraine's presidential administration said the two countries swapped 50 service personnel on Thursday.