The Muslim-led Bosnian government may be sensing victory in the aftermath of today's push even further into Serb territory. The offensive threatened a vital Serb supply line, near Sarajevo, which connects far-flung Serb-held territories. At the same time, they're pursuing a significant northwest offensive, sending 10,000 Serbs fleeing in their wake. The refugees "are completely shocked, stunned by the turn of events," says Peter Kessler, a spokesman for the U.N. High Commissioner for Refugees. Meanwhile, Serb leaders are scrambling to retaliate, vowing a speedy, major military response, and are already firing on civilians. Over the weekend shells rained on a Sarajevo suburb, killing two and injuring seven.Meanwhile, the U.S. -- which has threatened tolift an arms embargoagainst the Bosnian Muslims -- isn't likely to interfere. "It's hard to imagine the U.S. participating in that kind of an action against Bosnian government forces when they clearly have been the overwhelming victim in the aggression by the Bosnian Serb forces," a State Department official said.