The European Union should not sign a cooperation pact with Serbia until former Bosnian Serb military commander Ratko Mladic is arrested and delivered to the international war crimes court, the tribunal's chief prosecutor Carla del Ponte said Tuesday, according to dpa. Del Ponte, speaking at a conference in Brussels, said that only four war crimes fugitives, including Mladic and Bosnian Serb political leader Radovan Karadzic, were still at large. "They need to be brought to justice as soon as possible ... only if we manage to do so but will we be able to say we have completed our work," said Del Ponte. The war crimes prosecutor said EU demands that countries seeking closer relations with Brussels must establish full cooperation with the International Criminal Tribunal for the former Yugoslavia (ICTY) had been instrumental in the capture of key war crimes suspects. "EU conditionality is the most effective tool," said Del Ponte, adding that 90 per cent of those on trial in The Hague were there as a direct result of EU demands. As such, the 27-nation bloc must maintain pressure on Serbia, she insisted. "There should be no signing of a stabilization agreement with Serbia without the arrest and transfer of Mladic," Del Ponte insisted. Failure to do so would leave a "terrible legacy" for the region, she added. Mladic is charged with genocide over the 1995 Srebrenica massacre of 8,000 Bosnian Muslims. The EU suspended talks on the stabilization pact with Belgrade last spring, citing the country's failure to arrest Mladic and other war crimes indictees. But negotiations reopened in June after the arrest of Bosnian Serb general Zdravko Tolimir, a close Mladic aide. Signature of an EU stabilization agreement is the first step for countries seeking to join the bloc. EU countries are divided over whether to take a softer line with Belgrade in order to encourage cooperation on international plans to grant supervised independence to Kosovo, Serbia's breakaway province. Del Ponte is expected to end her term in mid-September but diplomats said she has been asked to stay on until the end of the year.