By Matt Prodger
BBC correspondent in Belgrade
The Chief United Nations war crimes prosecutor, Carla Del Ponte, says the Hague war crimes tribunal has for the first time decided to hand over to Serbia and Montenegro a case to be tried domestically.
The identity of the accused is expected to be announced on Monday, when she meets senior government officials.
Del Ponte says the process to bring people to justice is just starting
But it will be neither the Bosnian Serb general Ratko Mladic - one of Europe's most wanted men - nor any one of four former generals currently topping the list of Hague indictments.
She may visit only once every few months, but Carla Del Ponte is one of the most famous people in Serbia and Montenegro.
Her outspoken criticism of Belgrade's failure to deal with war crimes cases has angered many in a country which still struggles to accept Serbs as perpetrators and not just victims in the Balkan wars of the 1990s.
She arrived in Belgrade to address a conference of legal experts and human rights activists.
As the conference began - amid heavy security - several dozen demonstrators bearing posters of the former Yugoslav President Slobodan Milosevic, who is currently on trial at The Hague, protested outside the venue.
Protesters waving Milosevic posters were waiting for Ms Del Ponte
But the Foreign Minister of Serbia and Montenegro, Vuk Draskovic, sounded a different note, telling delegates that "the truth cures even when it hurts... the dead can't speak and the living are keeping silent, but reconciliation will not happen until everyone speaks about their sins.''
It is an impressive message, but at odds with the actions of his own government, which has yet to hand over more than a dozen war crimes suspects indicted by the Hague war crimes tribunal, among them Ratko Mladic, accused of responsibility for the massacre of more than 7,500 Muslim men and boys at Srebrenica in 1995.
Prosecutors say he is protected by members of the military in Serbia and Montenegro. The government here says he cannot be found.
The nationalist Prime Minister of Serbia, Vojislav Kostunica, says suspects should be tried by domestic courts, and not at The Hague.
Now prosecutors from the Independent Criminal Tribunal for the Former Yugoslavia (ICTY) have decided to hand over for the first time what Serbian court officials describe as a "significant'' case. It is seen as a vote of confidence in the special court set up in Belgrade last year to try war crimes cases.
In March it began the trial of six men accused of killing some 200 civilians in the Croatian town of Vukovar in 1991. The so-called Ovcara case has in fact proceeded slowly, and the most senior soldiers accused of the massacre are in any case standing trial at The Hague, not in Belgrade.
But Carla Del Ponte said the Belgrade political authorities had been less impressive.
The government has failed to hand over four former military and police generals, three of whom have been living openly in Serbia.
And in another incident that further soured relations between The Hague and Serbia and Montenegro, a suspect wanted for war crimes in Croatia, Goran Hadzic, went on the run in July just hours after a sealed indictment was delivered to Belgrade. He was apparently tipped off.
All this means that the union of Serbia and Montenegro is risking a return to international isolation, according to senior United States diplomats Marc Grossman and Pierre-Richard Prosper, who met with the prime minister and president of Serbia on Thursday.
The union's possible membership of Nato's Partnership for Peace programme is explicitly dependent on it handing over Mr Mladic, and it is unlikely to get past the very first stage of integration into the European Union unless it does more to co-operate actively with the Hague.
The ICTY is starting to wind up. After 2004 there will be no new indictments, by 2008 all trials should be finished, and by 2010 the appeals process completed.
And yet, Carla Del Ponte said, "Serbia and Montenegro is only at the beginning of the process which has to bring those responsible for atrocities elsewhere to justice".