SARAJEVO (Reuters) - Bosnia will hold presidential and parliamentary elections on Oct. 7, even though rival ethnic leaders have yet to agree on voting rules for the upper house of the Bosniak-Croat Federation’s parliament.

FILE PHOTO: Election Commission officials count votes in the central Bosnian town of Zenica October 12, 2014. REUTERS/Dado Ruvic/File Photo

Nearly 3.4 million voters will choose Croat, Serb and Bosniak members of the tripartite presidency and lawmakers for parliament’s lower house, plus regional leaders and assemblies, the Central Election Commission (CIK) said on Tuesday.

But CIK chief Irena Hadziabdic warned: “We are entering the election period without clear regulations on how to carry out elections and contrary to the international principles.”

Days after the European Union said Bosnia risked sliding into a constitutional crisis, she said Federation institutions could cease to operate unless a solution to the dispute over voting rules is found.

“Unless we ... reach a solution within a legal time-frame, we are facing a major problem,” Hadziabdic told a news conference.

The Balkan country has been governed along ethnic lines since a 1995 peace deal ended a four-year-long war that claimed 100,000 lives. The accords split Bosnia into two autonomous regions, the Serb Republic and the Bosniak-Croat Federation, which are linked via a weak central government.

Christian Croat and Muslim Bosniak political parties are currently deadlocked over amendments to the law on voting for the upper house of parliament of their joint Federation.

Responding to an appeal by Croat nationalists, Bosnia’s Constitutional Court ruled in 2016 that candidates elected to the upper house should come from main parties that draw the support of most of their respective ethnic kin.

Croat parties have since proposed new, ethnically-based electoral districts where people would vote only for their own community’s representatives at all levels of governance including the presidency.

They say they want to prevent Muslim Bosniaks, the majority group in the Federation, from bringing about the election of Croats of a civic, non-nationalist persuasion they see as not serving the best interests of Bosnian Croats.

But Bosniak parties oppose their proposals, fearing they could be a maneuver to forge a separatist Croat entity reminiscent of Bosnia’s devastating 1992-95 war.

Western envoys have been mediating talks between the parties but no breakthrough has been made. The EU last week warned Bosnian leaders not to hold the election results “hostage to party interests”.

Bosnian Serb, Bosnian Croat and Muslim Bosniak leaders have heated up nationalist rhetoric recently, launching election campaigns unusually early and halting reforms needed for Bosnia to progress towards membership of the EU and NATO.