The European Union could use proceeds from frozen Russian assets to help Ukraine within a few months under a plan that includes buying arms for Kyiv.
Leaders of the bloc's 27 member countries agreed at a summit in Brussels to move ahead with work on the plan, presented this week by the EU's executive body, the European Commission.
"I am confident that we can act very quickly," Charles Michel, president of the European Council of EU leaders, told reporters.
The leaders' desire for urgency reflects increasing alarm about the war in Ukraine, with Kyiv's ammunition-starved forces struggling to hold back Russian troops and a $US60 billion military aid package for Kyiv stuck in the US Congress.
European Commission President Ursula von der Leyen said the first 1 billion euros ($A1.66 billion) from the scheme could be disbursed as soon as July 1.
Ukrainian President Volodymyr Zelenskiy had earlier urged the EU leaders to go ahead with the plan.
"Russia must feel the real cost of war and the need for a just peace," Zelenskiy told the EU leaders via video link, backing a proposal he said was "only fair".
Zelenskiy said it was "humiliating for Europe" that Ukraine did not have enough artillery in its fight against Russia, which invaded its neighbour in February 2022.
He urged the EU to use not only the profits of the frozen assets but also the assets themselves - something the EU is not considering.
The Commission has proposed transferring 90 per cent of profits from the frozen Russian assets to an EU-run fund used to finance arms for Kyiv. The other 10 per cent would go to budget aid for Kyiv.
The Commission estimated the profits on the assets - various Russian central bank securities and cash - could be between 2.5 billion euros ($A4.16 billion) and 3 billion euros per year.
EU heavyweights Germany and France voiced strong backing to the plan.
But using the money to buy weapons is problematic for some countries, including neutral militarily non-aligned countries such as Malta, Austria and Ireland.
"For us neutrals it must be ensured that money, for which we give our approval, is not spent on weapons and ammunition," Austrian Chancellor Karl Nehammer said.
Michel said the EU could find ways to take into account their concerns as part of the scheme.
Russia said on Thursday its artillery shell production had soared over the past year.
On Wednesday, it described the EU plan as banditism and theft.
"We must make sure that this is, from a legal point of view, extremely well thought through," Luxembourg Prime Minister Luc Frieden said.
Some European banks are lobbying against the proposal, fearing it could lead to costly litigation, industry sources said.
The bloc's 27 leaders will also debate how European countries can do more to defend themselves and boost their arms industry, reflecting fears that Russia will not stop at Ukraine and the United States may not be such a staunch protector of Europe in future.
"Now that we are facing the biggest security threat since the Second World War, it is high time we take radical and concrete steps to be defence-ready and put the EU's economy on a 'war footing'," Charles Michel, president of the European Council of EU leaders, said.
