Montenegro, July 18, SPA -- NATO Secretary-General Jaap de Hoop Scheffer on Monday was expected to press for the arrest of top war crimes suspect Ratko Mladic. The extradition of the Bosnian Serb wartime commander to the U.N. war crimes tribunal in The Hague, Netherlands, remains a key condition for Serbia-Montenegro to join NATO's Partnership for Peace _ an outreach program considered a stepping stone to full alliance membership. De Hoop Scheffer was in Belgrade for talks with Svetozar Marovic, president of Serbia-Montenegro, Foreign Minister Vuk Draskovic and Serbian President Boris Tadic, according to a report of The Associated Press.