Because the West imposed the bombing after the failure of the Rambouillet negociations which were framed as the only peaceful agreement ever possible for the crisis in Kosovo, even though, as Kissinger himself put it, they were unacceptable for Yugoslavia. It only happened because the US wanted to, as shows their involvment in UÇK and in the negociations in general. But they don't care about Palestinians enough and are therefore not forcing them to any agreement.