The Netherlands says it will refuse to back a major European Union trade and aid agreement with Serbia until Belgrade fully cooperates with the U.N. War Crimes Tribunal.

EU leaders are meeting Monday in Brussels on the Stabilization and Association Agreement with Serbia. The deal is a major step toward possible EU membership. It requires the approval of all 27 members.

EU Enlargement Commissioner Olli Rehn says members should sign the agreement soon to send what he calls a very strong signal that Serbia has a European future. He also says Serbia's cooperation with the tribunal should be a condition for ratification.

But Dutch European Affairs Minister Frans Timmermans says his country will not even sign the pact until there is full cooperation. The Netherlands insists that Belgrade catch and surrender fugitive war crimes suspects Radovan Karazic and Ratko Mladic.

Supporters of an early deal with Belgrade say it could boost the prospects of the country's pro-Western President Boris Tadic to win next month's runoff presidential election. He faces nationalist Tomislav Nikolic, who favors closer ties with Russia.

Some information for this report was provided by AFP, AP and Reuters.