Latvia ? NATO leaders on Wednesday invited their old enemy Serbia – along with Montenegro and Bosnia-Herzegovina – to join a program considered a first step toward eventual membership in the alliance.

They urged Serbia and Bosnia, however, to fully cooperate with the U.N. war crimes tribunal.

The two Balkan neighbors were earlier excluded from NATO’s Partnership for Peace outreach program because of their failure to apprehend the most wanted war crimes suspects indicted by the U.N. tribunal for the former Yugoslavia – former Bosnian Serb leader Radovan Karadzic and his wartime military chief, Gen. Ratko Mladic.

But NATO said at the end of a two-day summit that the three countries can offer a “valuable contribution” to stability in the Balkans, and that their membership in the program was important for the region. The program includes many former Eastern bloc countries and is considered a stepping stone toward full NATO membership.