SARAJEVO - A Muslim leader in Bosnia has warned that his Bosnian Serb counterpart is "playing with fire" by planning a controversial referendum on when the country's Serbs celebrate their national day.

Earlier this month, Bosnian Serb lawmakers stirred controversy by announcing a referendum would be held in September - a week before local elections - on whether to keep celebrating their statehood day on January 9, a contentious date in the eyes of Bosnia's non-Serb communities. Since the end of the 1992-1995 war, Bosnia has been divided into two semi-independent entities - one run by Serbs, and a Muslim-Croat Federation. Bosnian Muslim leader Bakir Izetbegovic told AFP that Bosnian Serb President Milorad Dodik was "playing with fire" by holding a referendum on the contentious issue, which is slated for September 25.

"He always tries to... push the line of what is allowed in this country and what is acceptable for the international community," Izetbegovic stressed. "If he crosses the line, it will not be without consequences," Izetbegovic said.

Dodik has repeatedly threatened to organise a referendum on the independence of the Serb part of Bosnia - the Republika Srpska.

The planned referendum also defies a court order ordering that the date when Bosnian Serbs' mark their national day be changed out of respect for Bosnia's other groups, particularly as it coincides with an Orthodox holiday.

Izetbegovic filed a formal protest against the January 9 celebrations at the constitutional court in 2013, arguing that it left out Bosnia's other groups.

The court found in his favour late last year and ordered Republika Srpska to choose a date that would also be acceptable to the country's ethnic Croats and Muslims. Bosnian Serb political parties however rejected the court's ruling.

Izetbegovic said steps could be taken by Valentin Inzko, the international envoy to Bosnia, to prevent the referendum, which is against the Dayton peace deal that ended the 1992-1995 war.

Austria's Inzko has the power to sack elected officials and impose laws.

Izetbegovic warned that the referendum threatened "principles set up 21 years ago... which enabled peace in this country."

And he said there was a "political motivation" for holding the referendum just a week before local elections.

Voters in the September 25 referendum will be asked: "Do you support that the Day of Republika Srpska be marked and celebrated on January 9?"

On that day in 1992, Bosnian Serbs proclaimed the so-called "Republic of Serbian people" at a time when Bosnia was still part of the former Yugoslavia. Bosnia's other communities took it as a sign that Bosnian Serbs were not interested in a united Bosnia.

Three months later marked the start of a war that pitted Muslims and Croats against Serbs and then Muslims against Croats, claiming some 100,000 lives overall.

Of Bosnia's 3.5 million inhabitants, 1.2 million live in Republika Srpska where ethnic Serbs make up nearly 82 percent of the population.