SARAJEVO (Reuters) - Bosnia risks sliding into constitutional crisis if rival ethnic groups in the country fail to resolve a row over voting rules before autumn elections, senior European Union officials suggested on Wednesday.

The Balkan country has since 1995 been governed under an often volatile power-sharing framework set as part of a peace accord in that year that ended four years of war.

Its electoral commission is next week expected to announce presidential and parliamentary ballots for October, but the voting law dispute has created so far unbridgeable rifts between the Christian Croats and Muslim Bosniaks in the autonomous Federation they jointly rule.

EU foreign policy chief Federica Mogherini and EU enlargement commissioner Johannes Hahn said holding the election results “hostage to party interests” was not an option.

“We expect the leaders of Bosnia and Herzegovina to reach a compromise... If the results of the general election cannot be implemented, the formation of a new government could be at risk,” they said in a statement that echoed concerns voiced by the electoral commission.

Last year, a Croat parliamentary bloc proposed restricting people in some electoral districts to voting for their own community’s representatives at all levels of government, a move that Bosniak parties rejected.

There are few signs of a workable compromise emerging from a final round of talks between the two sides scheduled for Thursday.

Croat nationalists say they want to prevent Muslim Bosniaks, the majority group in their joint federation, from facilitating the election of Croats of non-nationalist persuasion.

Bosniak parties fear the proposal could be a prelude to the Croats forging a separatist entity.

During the war, Bosnian Croats and Serbs fought to carve out ethnic statelets and drove out rival communities, mainly Bosnian Muslims, leaving 100,000 people dead and about two million homeless.

Bosniaks and Croats formed a joint federation under the peace deal, which also granted Serbs their own autonomous entity within Bosnia.