Ahead of Sunday's referendum in Bosnia's Serb mini-state has turned into a proxy political battle between the West and Russia, stoking ethnic tensions and triggering fears of new clashes more than 20 years after the end of the Balkans War. The referendum also reflects the wider tensions between Western nations — which are supporting the Bosniaks and Croats — and Russia, which is backing the Serbs.Despite a ruling of Bosnia's constitutional court that the date discriminates against non-Serbs, the referendum will decide whether the Day of Republika Srpska can continue to be celebrated on Jan. 9, the day the Serb-dominated entity was formed just before the outbreak of the war in 1992.The vote sparked wider tensions etween Western nations which are supporting the Bosniaks and Croats and Russia, which is backing the Serbs. The U.S. embassy in Sarajevo threatened unspecified "consequences" if the referendum is not canceled, while the Russian ambassador openly supported the referendum, saying it is an act of democracy. Russia is a traditional backer of Orthodox Slavic Serbs. EU High Representatives warned Republika Srpska of not holding a referendum. Yet, Bosnian Serbs didn't respect the Constitutional Court's decision and celebrated the day despite the ban.Bosnian Serb leader Milorad Dodik, who initiated the referendum and went to Moscow to meet President Vladimir Putin this week, called Bosniak reactions "hysteria." "This is not a referendum about secession as many want to portray it," he said. "It is not even a beginning of such a process."International officials overseeing Bosnian peace accords were outraged by Dodik's defiance and threats of new clashes. "In the past 20 years we have not heard such language," said the High Representative for Bosnia, Austrian diplomat Valentin Inzko.The Peace Implementation Council, an international body overseeing Bosnia, said there will be no redrawing of borders and called on everybody "to refrain from reactive measures and divisive rhetoric." It also urged the Bosnian Serbs to cancel the vote, but Council member Russia distanced itself from the statement.The referendum planned for Sept. 25 will be conducted on the initiative of the government of the Republika Srpska. Bosnia's Serb-dominated entity, Republika Srpska, is one of Bosnia and Herzegovina's two constituent entities, alongside the federation, with a Bosnian and Bosnian Croat majority. Both entities have their own government, parliament and judiciary. The Day of the Republika Srpska created tensions inside Bosnia because of its connection to the entity's secessionist ambitions. It is also ruled as contrary to the Dayton treaty, the peace agreement that ended the war in 1995. Apart from challenging the country's rule of law, Bosniaks also fear this referendum is a test for a more serious one in 2018 on independence which would not go down peacefully, officials in Sarajevo warned.