A group of four countries have relaunched the push to unlock immobilised Russian assets to fund Ukraine's budgetary and military needs before European Union member states become distracted by their own domestic elections.

The EU holds €210 billion of these assets, most of it in Belgium.

"Ukraine needs more financial support in both the short and long term. The EU, in dialogue with its partners, should continue to provide comprehensive, predictable and structured financial support to Ukraine in line with its need," the letter reads.

The letter was led by Sweden and co-signed by the Netherlands, Spain and Poland, a selection meant to represent Northern, Western, Southern and Eastern Europe.

It is addressed to High Representative Kaja Kallas and Irish Foreign Minister Helen McEntee, as Ireland currently chairs the Council's rotating presidency.