The anniversary of the start of the conflict, which has killed hundreds of thousands of people and ravaged swathes of Ukraine, comes a day after Hungary vetoed new EU sanctions against Russia and a 90 billion euro ($A150 billion) loan critical to Ukraine's survival.
Hungary, which maintains close ties with Moscow, and neighbouring Slovakia accuse Kyiv of deliberately blocking supplies of Russian oil via the Druzhba pipeline, which Ukraine says it is trying to repair after a Russian strike in January.
President Volodymyr Zelenskiy, facing mounting US pressure to secure a peace deal, has repeatedly urged Kyiv's allies to tighten sanctions on Moscow and send more weapons as Russian President Vladimir Putin shows no signs of ending his war.
European Commission President Ursula von der Leyen condemned Russia for damaging the pipeline but said the EU has asked Ukraine to speed up repairs.
Officials including von der Leyen, Finnish President Alexander Stubb and Danish Prime Minister Mette Frederiksen travelled to Kyiv for the anniversary on Tuesday, but were not joined by heads of major Western governments.
Leaders present in Kyiv met as the "Coalition of the Willing". British Prime Minister Keir Starmer, taking part by video link, said Ukraine's allies would have to "do the hard yards" of helping Kyiv and pressuring Russia.
Britain on Tuesday sanctioned the oil pipeline giant Transneft among nearly 300 other Russian targets, in what it called its largest package of measures since the early months of the war.
"We know that when it comes to talks, there's one person standing in the way of progress in those talks, and that is Putin, and nobody but Putin," Starmer said.
German Chancellor Friedrich Merz, also joining remotely, said it was critical to "dry up Russia's war funding" by pushing through a 20th package of sanctions.
Brussels plans to submit a legal proposal to ban Russian oil imports permanently on April 15, three days after a parliamentary election seen as the main obstacle to Hungarian agreement, according to EU officials and a document seen by Reuters.
And in Kyiv, von der Leyen said the EU would deliver on its 90 billion euro loan for Ukraine, "one way or the other".
In televised comments, Putin accused Ukraine of trying to torpedo the peace process, which is stalled over the issues of territory and control of Europe's largest nuclear plant.
Separately, Russia's foreign intelligence service said Britain and France were "actively working" with Ukraine to help it obtain nuclear weapons to secure more favourable terms in a peace deal.
It provided no evidence for its claim, which was swiftly denied by Kyiv, London and Paris.
Zelenskiy said in a morning address the nation would not betray the sacrifices made by its people just to bring an end to the conflict. "We cannot, we must not, give it away, forget it, betray it."
In a televised address to the European Parliament, Zelenskiy urged members of the 27-nation EU to keep defending the European way of life, saying EU membership would be a guarantee of Ukraine's future security after a peace deal is signed.
"Russians must learn that Europe is a union of independent nations and millions of people who do not tolerate humiliation and will not accept violence," Zelenskiy said.
He also invited US President Donald Trump. "Only by visiting Ukraine and seeing our lives and struggles with your own eyes, by understanding our people and the enormity of their pain, can you see what this war is really about," he said.
