(29 Aug 1997) English/Nat The White House has warned Bosnian Serb leaders that it will hold them responsible for acts of violence against peace-keeping forces in the country. Friday's statement came after supporters of war crimes suspect Radovan Karadzic were blamed for throwing stones at S-FOR troops in the northern town of Brcko. While U-S President Bill Clinton was busy Friday trying to drop his handicap while on holiday at Martha's Vineyard, the situation in Brcko was being closely followed.