SARAJEVO: The U.S. will meet Friday in Rome with the three Balkan presidents and NATO representatives in an effort to diffuse mounting tensions that threaten an already fragile peace accord. At issue is the Serb contention that they are being unfairly singled out for war crimes violations. Stung by the capture and extradition to The Hague of two Serb army officers accused of war crimes, Bosnian Serb leaders have broken off all contact with the NATO peacekeeping force and have warned all Serbs not to cross into Muslim-held areas of Sarajevo. Bosnia's Muslim government is still holding out for more Serbs accused of war crimes, and in retaliation, Serbs have reportedly arrested three Muslims suspected of killing Serb civilians. Mounting suspicions on all sides have translated into more restrictions and controls for people crossing supposedly open borders, says U.N. aid agency spokesman Kris Janowski. Draft-age men are also being prevented from crossing at some checkpoints, he said. In this atmosphere, the challenge for the U.S. and its allies in Rome will be to cool passions ignited by the arrests and reach an agreement that will ensure prosecution for war crimes without destroying the fragile federation between Serbs, Muslims and Croats in Bosnia.