Belgian Prime Minister Bart De Wever has asked other EU leaders to guarantee they will share the risks if frozen Russian assets, held in his country, are used to finance loans to Ukraine.

At a summit in Copenhagen, many European Union leaders expressed support for the idea of using Russian assets frozen in the West to provide a 140 billion euro ($A249 billion) loan to Ukraine.

However, legal and financial aspects remained to be settled.

International law forbids the confiscation of sovereign assets, so the EU would have to find a way to continue to recognise Moscow's claim on its central bank assets and to protect Belgium, where most of the assets are located, from Russian retaliation.

"There's no free money. There are always consequences," De Wever told reporters in Copenhagen on Thu

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