BRUSSELS A European Commission proposal to use frozen public Russian assets to help finance Ukraine will not be published until September, a spokesman said on Thursday.

A proposal was initially expected before August.

The European Union, which first floated this idea in November, is focused on finding a legal way to use the tax on the interest made by these assets for Ukraine. The EU is being careful to make sure the method holds up in court in the event of any lawsuits.

The EU has frozen over 200 billion euros ($223.70 billion) of Russian central bank assets since Russia's invasion of Ukraine, with the bulk held in Belgium. The EU has also frozen privately held funds and legal pushback has already started.

Russian billionaire Roman Abramovich, who was placed on the EU sanctions list, has mounted a legal challenge along with one of Russia's oldest asset managers, First AM, which is claiming $2 billion on behalf of its clients from Belgium's clearing house Euroclear and which also holds much of Russia's public frozen money.

The spokesman added that the EU was working on an agreement with the Group of Seven (G7) countries on how to move forward and a statement was expected this month. G7 countries and the EU have frozen over 300 billion euros ($335.55 billion) combined.

"Discussions between member states have been going well. The last meeting of the council working party on this matter was on July 12 and the next one will take place in September," the spokesman told reporters.

"Intensive work is taking place in the G7 context and we aim to have a G7 statement before the summer break. A legal proposal we aim to have after the summer break."

($1 = 0.8941 euros)

(Reporting by Julia Payne; Editing by Sharon Singleton)