NPR's Mara Liasson reports that President Clinton and the leaders of 40 other nations met today in the Bosnian capital, Sarajevo, to sign the Balkan Stability Pact. The document commits western nations to encourage trade and investment in the Balkans. Regional governments pledge to make the political and economic reforms necessary to encourage investment. One government was conspicuously absent — that of Yugoslav President Slobodan Milosevic. The summit leaders made clear they will withhold all but humanitarian aid from Serbia, as long as Milosevic remains in power.