Brussels on Tuesday asked EU member states to provide 50 billion euros more to support Ukraine over the next four years, as part of a boost to the bloc's budget.

"This financial reserve will allow us really to calibrate our financial support according to the evolution of the situation on the ground," European Commission chief Ursula von der Leyen said.

The proposal from the European Commission, the EU's executive arm, is aimed at helping prop up Kyiv's finances and covering immediate reconstruction costs caused by the Russian-Ukrainian war.

The money, a combination of grants and loans, is part of the review to plug gaps in the EU's budget for the period 2024-2027 left by the fallout of the COVID-19 pandemic and the conflict.

It represents less each year than the 18 billion euros the EU has committed toward Ukraine government expenditures in 2023.

Overall, the EU has already committed 30 billion euros from its budget to support the country since the beginning of the Russian-Ukranian war in February 2022.

The money for Ukraine is expected to be dependent on reforms to strengthen its judiciary and tackle corruption that are intended to spur Kyiv along the path to joining the EU.

The proposal comes ahead of a major donor conference in London this week on paying for Ukraine's reconstruction.

The World Bank in March estimated Ukraine's long-term reconstruction costs at over 380 billion euros.

As part of its budget review, Brussels is also asking for 15 billion euros more to help deal with immigration and 10 billion euros to subsidize key industries.

But the demands for a fresh injection of money will face some serious headwinds from EU countries still grappling with the consequences of the pandemic and war.

All 27 member countries have to agree to increase the budget.

"We are fully aware of the fact that member states were also hit by the crises and after years of large public support to their economies it is now time for them for consolidating," von der Leyen said.

"We come today with a very targeted and limited proposal for the absolute must."