Bosnian Serb leaders today promised former President Jimmy Carter they would agree to a four-month ceasefire in the war with Bosnian Muslims, as well as discuss an international peace plan under the aegis of the U.S., Russia, Britain, Germany and France. After several hours of talks with Bosnian Serb leader Radovan Karadzic in the town of Pale, Carter said he now plans to take his olive-branch-for-hire diplomacy to the Muslims in Sarajevo. Carter began the talks over the weekend even though the Serbs had already broken promises made just days before that made up the conditions for his visit. (U.N. officials, for example, reported that Serb forces attacked peacekeepers and civilian targets in Sarajevo, blocked U.N. convoys and expelled more civilians from Serb-held territory -- contradictions of Karadzic pledges.) TIME Central European bureau chief James L. Graff says Carter's presence is now merely condoning their old habits. "It's not like there's a whole lot Carter can derail, because there's not a lot there. But he's got to be careful, because so many people have been walked around the block by the Serbs," Graff said.