SARAJEVO (Reuters) - Separatists pushing to split up Bosnia along ethnic lines could endanger its bid to join the European Union and force international powers to intervene, the peace envoy for Bosnia has told Reuters.

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The EU accepted Bosnia’s application to join three months ago and last week took the first step in what is certain to be a long accession process. But recently Serb and Croat nationalists have intensified calls to divide the country along ethnic lines.

“We have on one side integration into Europe and at the same time disintegration at home,” said international High Representative Valentin Inzko, whose office has helped maintain unity in Bosnia since the 1992-95 war.

“It can happen that the country will slow down its process even towards Brussels because disintegration could be stronger than integration,” he said.

“We would intervene if red lines are crossed, if they (the Bosnian Serbs) announce a referendum on independence - this would be such a red line.”

Under the Dayton peace agreement which ended the war, Bosnia was split into two autonomous regions - the Serb-dominated Serb Republic and the Federation dominated by Muslim Bosniaks and Croats - linked via a weak central government.

Bosnian Serb nationalist leader Milorad Dodik has already said the EU accession process will depend on meeting Serb political goals. He has threatened the secession of the Bosnian Serb region and favors closer ties with Russia.

Bosnian Croat leaders have revived the notion of their wartime para-state Herceg-Bosna, and proposed the division of the country into three or more federal units based on majority populations.

The high representative has wide-ranging powers to act against violations of the Dayton agreement, which is designed to preserve Bosnia as a single state with Sarajevo as its undivided capital.

Asked about the possibility of a military intervention in the case of secession, Inzko said he would rather stick to peaceful solutions such as international pressure.

Previous high representatives, who include Carl Bildt and Paddy Ashdown, have taken action including firing a total of 180 officials.

But some Western diplomats have said that in the case of the Bosnian Serb secession, Inzko would be authorized to invite foreign troops to prevent an armed conflict.

Some 200 soldiers of the EU peacekeeping mission EUFOR are still stationed in Bosnia.

The envoy’s powers are vested in him by the Peace Implementation Council, a body consisting of representatives of major world governments and international institutions, including the United Nations and the European Union.