The International Court of Justice (ICJ) in The Hague is to announce its ruling on genocide cases between Croatia and Serbia, the BBC reports.
The Croatian government has alleged that Serbia committed genocide in the town of Vukovar and elsewhere in 1991.
Serbia later filed a counter claim over the expulsion of more than 200,000 Serbs from Croatia.
About 20,000 people died during the 1991-1995 war, when Croatia broke away from Yugoslavia.
Croatia filed its initial case with the ICJ – the top UN court – in 1999, accusing Serbs of targeting ethnic Croats during the conflict.
The town of Vukovar was devastated when it was occupied by Serbs in 1991.
Croatia also wants Serbia to pay compensation for damages “to persons and properties as well as to the Croatian economy and environment”.