The warning came only two weeks after U.S.-hosted talks in Washington failed to find a compromise agreement between Dodik and his Muslim rival, Haris Silajdzic, on key reforms that the European Union demands as a prerequisite for closer ties.

"We say to Mr. Silajdzic and his supporters not to play with fire," Dodik said in a statement, responding to a renewed challenge by Silajdzic to the legitimacy of the Serb Republic and its right to exist as an autonomous entity.

"If they continue with grave offences, humiliation and underestimation of the rights and interests of the Serb people in Bosnia, every possibility of co-existence and common future will be destroyed," Dodik said in his toughly worded statement.

U.S. officials expressed concern at the volatile climate in Bosnia, where stability could be threatened by an angry Serb reaction to the imminent U.N. decision on the fate of Serbia's breakaway Kosovo province. "We are here to help but Bosnian citizens themselves must say that the behaviour of your politicians who use inflammatory rhetoric is unacceptable," U.S. State Department Deputy Assistant Secretary Rosemary Di Carlo told reporters.

Dodik was reacting to an interview with the BBC this week, in which Silajdzic said the Bosnian Serb Republic was built on genocide in the 1992-95 war and should not be recognised by the international community.

DIVIDED BY AGREEMENT

The U.S.-sponsored Dayton peace agreement divided Bosnia into two autonomous regions, the Muslim-Croat federation and the Serb Republic. But the country's two parts are still deeply divided by memories of the war in which up to 150,000 died. Silajdzic was a signatory to Dayton but since coming to power in an October 2006 election his main activity has been to call for the abolition of the Serb Republic.

Analysts say the political situation in Bosnia is reminiscent of the period preceding the war, with animosity between the two regions and peoples steadily on the rise since two leaders seem incapable of agreeing on a single issue.

Last year, Dodik threatened to hold a referendum on the secession of the Serb Republic if its existence was jeopardised. He later dismissed the threat as an election campaign line. Dodik has also flirted with comparisons between the Serb Republic and Kosovo, saying if the Albanian majority in the U.N.-run Serbian province win independence from Serbia, Bosnian Serbs may seek the same from Bosnia.

"They can think whatever they want about the Serb Republic. Until they realistically accept it and us as well, they will not be able to make any deal, even if Bosnia is stopped on its way to the EU for the next 100 years," he told journalists on Wednesday

Bosnia's talks on closer ties with Europe have been stalled over disagreement on how to reform the country's ethnically separate police forces and change the constitution to fit requirements for European integration.