The Croatian police are threatening to call off Saturday's World Cup football qualifier between Croatia and Serbia in Zagreb if home fans resort to anti-Serbian chanting.
Police say ethnically-based and insulting chants would not be tolerated.
Croatia and Serbia meet in a football match for the first time as independent nations since the bloody civil war fought between the two former Yugoslav republics in the 1990s.
Serbian fans have been banned from the stadium following an agreement between the two countries' football federations in a bid to avoid crowd trouble.
