Seven years after NATO's air campaign to end Serbia's crackdown on separatist ethnic Albanians in Kosovo, President Boris Tadic will sign up to the military alliance's Partnership for Peace program.

Accompanied by Secretary General Jaap de Hoop Scheffer and the 26 NATO ambassadors at Brussels headquarters, Tadic will set his troubled country on the long and once-unlikely path toward membership.

It is hoped that the move will pull the rug out from under hard line nationalists -- who helped tear the former Yugoslavia apart in the 1990s and left Serbia economically hobbled -- ahead of the January 21 general election.

Serbia topic at EU summit

Yet European Union leaders, who meet at a two-day summit starting later on Thursday, will remind Serbia that it must bring in former Bosnian Serb military chief Ratko Mladic before talks on closer ties with the EU can resume.

In May, the 25-member block froze a Stabilization and Association Agreement -- a first step toward joining the EU -- over Serbia's failure to fully cooperate with the International Criminal Tribunal for former Yugoslavia (ICTY).

In draft conclusions prepared for their two-day summit, the leaders reaffirmed "the EU's continued engagement with, and support to, Serbia."

"The European Council recalls that the EU is ready to resume and conclude the negotiations for a Stabilization and Association Agreement as soon as full cooperation with (ICTY) is achieved."

NATO's decision last month to open its doors to Serbia came as a surprise as it too had insisted on cooperation with the ICTY, which has indicted Mladic, as well also Bosnian Serb wartime political leader Radovan Karadzic.

The two are wanted for genocide, war crimes and crimes against humanity.