By Daria Sito-Sucic and Gordana Katana
SARAJEVO/BANJA LUKA, Bosnia (Reuters) - Bosnia's autonomous Serb entity is set to defy its highest court with a referendum on a national holiday on Sunday that may stoke separatist sentiment lingering since the 1990s war.
The referendum, on whether to mark Jan. 9 as "Statehood Day" in the Serb Republic part of Bosnia, will be the country's first since a 1992 plebiscite on secession from then-Yugoslavia that ignited three years of ethnic war in which 100,000 were killed.
The Sarajevo-based Constitutional Court ruled on Saturday that this "Statehood Day" was illegal since it coincides with a Serbian Orthodox Christian holiday and so discriminated against Muslim Bosniaks and Catholic Croats living in the Serb Republic. The court also banned the planned referendum.
Jan. 9 was the day in 1992 when Bosnian Serb legislators declared the creation of an independent Serb Republic after Bosniaks and Croats voted for independence from Serbian-dominated federal Yugoslavia.
Many believe that by defying the court ruling, Milorad Dodik, the current Serb Republic's nationalist president, aims to highlight the weakness of Bosnia's central authorities in Sarajevo and set the stage for a vote on secession.
The court's rulings are formally binding, but more than 90 of them have been ignored by the autonomous regions that were set up by negotiators to hold Bosnia together after the war.
The United States, which brokered the 1995 Dayton peace deal, and Aleksandar Vucic, prime minister of neighboring Serbia, have all warned of the risk of renewed instability in the economically deprived Balkan region. The European Union also opposes the Serb referendum.
But President Vladimir Putin of Russia, a traditional ally of the Bosnian Serbs, has endorsed the referendum, and invited Dodik to Moscow for consultations on Thursday.
ETHNIC WAR IN 1990s
The Bosnian Serbs' rejection of an independent, multi-ethnic Bosnia in 1992 triggered an avalanche of bloodshed in which Serbs and Croats carved ethnically pure statelets out of Bosnia with the backing of kin in neighboring Serbia and Croatia.
It was Europe's bloodiest conflict since World War Two.
Zeljko Kovac, an unemployed war veteran from the largest Bosnian Serb city, Banja Luka, said he would vote for Statehood Day "because I fought for the Serb Republic".
"We will not take orders from Muslims on what we are going to celebrate," Kovac told Reuters, echoing a widespread belief among Serbs that the Sarajevo court is biased against them.
The U.S. Embassy in Sarajevo said that pursuing the referendum in defiance of the high court posed a "threat to the rule of law and thus a threat to the stability, security and prosperity" of Bosnia.
"The Dayton Peace Agreement is an international peace treaty that cannot be challenged without consequences. We will not accept attempts to obstruct implementation of the DPA or weaken (Bosnian) institutions," the embassy said in a statement.
The ambassadors to the international peace implementation body for Bosnia urged the Serb Republic to cancel the referendum, but fell short of specifying what the consequences would be. Russia abstained from a joint statement.
The European Union believes strengthening Bosnia's complex, ethnically-balanced federation is essential for peace in a region still afflicted by ethnic tensions, and a precondition for its eventual membership of the EU.
EU foreign ministers this week accepted Bosnia's membership application, raising hopes in Sarajevo of eventual admission to the bloc.
(Editing by Thomas Escritt and Mark Heinrich)