Yugo Leader NPR's Michele Kelemen reports from Washington where Yugoslav President Vojislav Kostunica visited the White House today. President Bush told him that further U.S. assistance to Yugoslavia depends on Belgrade's cooperation with the Hague war crimes tribunal, which is seeking the extradition of Kostunica's predecessor, Slobodan Milosevic. Kostunica reiterated that his government should be given time to try Milosevic in Yugoslavia first, which will promote development of new civil institutions. The Hague tribunal's chief prosecutor has also been in Washington. Carla del Ponte says she and Secretary of State Powell agreed Belgrade should set a date for Milosevic's extradition.