Ukrainian President Volodymyr Zelensky signed an accord with the Council of Europe last year to create a legal body to prosecute the "crime of aggression" in the invasion Russia launched in 2022.

Becoming a founding member would allow the European Union to play a central role in its operations, including the selection of judges and prosecutors.

"Justice for the victims of aggression is the best route to lasting peace," said EU foreign policy chief Kaja Kallas.

"The pursuit of justice is equally a deterrent for would-be aggressors," she added.

The 46-member Council of Europe -- a France-based rights body -- is distinct from the EU.

Members include the EU's 27 countries but also key European states from outside the bloc such as Turkey, Britain and Ukraine.

Russia was expelled in the wake of its invasion of Ukraine and has already said it will disregard the special tribunal's rulings.

Kyiv and its supporters want to see justice served for Russia's war and European foreign ministers endorsed the creation of the judicial body in a meeting in May last year.

Brussels has already helped draft the tribunal's founding legal texts and contributed 10 million euros to prepare its operational set-up.

Its bid for founding member status needs to be approved by the EU's 27 nations, before submission to the Council of Europe.

"This is a decisive step towards establishing the Special Tribunal and ensuring that those responsible for Russia's crime of aggression are held to account," said EU justice commissioner Michael McGrath.

The tribunal, which was initially hoped could start work this year, could in theory try senior figures up to Russian President Vladimir Putin.

The International Criminal Court (ICC) in The Hague has already issued arrest warrants for Putin over the abduction of Ukrainian children and four of his top commanders for targeting civilians.

But the ICC does not have the jurisdiction to prosecute Russia for the more fundamental decision to launch the invasion -- otherwise known as the "crime of aggression".