The record of the UN in the Bosnia conflict was one of appalling feebleness in the face of repeated (mainly Serbian) aggression and human rights violations. The UN established five "safe havens" (one of them Srebrenica) in Bosnia in which the safety of the inhabitants (mainly Bosnian Muslims) was "guaranteed". When push came to shove, however, the UN stood idly by as Serb forces overran Srebrenica. The result was around 10,000 Bosnian Muslim males gunned down in cold blood with the remaining population being expelled.
The international force that eventually enters Kosovo may have the figleaf of UN approval but must be in essence Nato-led, otherwise it will not have the support or trust of the returning Kosovo Albanian deportees. The credibility of the UN in former Yugoslavia is zero.