BELGRADE, September 11, 2008 (AFP) - Serbia said Thursday it is 'determined' to arrest Bosnian Serb genocide suspect Ratko Mladic as the UN chief war crimes prosecutor left Belgrade optimistic about the case crucial to the country's EU aspirations.

President Boris Tadic told the visiting prosecutor, Serge Brammertz, that the 'new authorities in Serbia showed their firm determination' already by sending Mladic's wartime leader in Bosnia, Radovan Karadzic, to the UN war crimes tribunal in The Hague.

Serbia was 'fully aware of its international and domestic legal obligations to (ensure) that remaining fugitives must end up in The Hague,' said a statement from Tadic's office.

Brammertz was given the same message from Serbian Prime Minister Mirko Cvetkovic, whose government ordered the arrest of Karadzic in late July, around two weeks after it took office.

The International Criminal Tribunal for former Yugoslavia (ICTY) prosecutor expressed 'careful optimism' Wednesday that Serbia would locate and arrest the two remaining fugitives, Mladic and a Croatian Serb leader, Goran Hadzic.

Brammertz made the statement after meeting his Serbian counterpart Vladimir Vukcevic and a Serbian government 'Action Team' formed to focus on the search for the fugitives.

His meetings on Thursday 'also were held in a positive and constructive atmosphere,' the prosecutor's spokeswoman Olga Kavran told AFP prior to his departure from Belgrade following the two-day visit.

Belgrade expects Brammertz to provide a positive evaluation of its cooperation with the ICTY, a condition for the European Union to unfreeze a trade and aid pact with Serbia seen as a first step towards membership.

Brammertz is expected to brief EU officials in Brussels about the topic at a meeting of the 27-nation bloc's foreign ministers scheduled for Monday.

But earlier on Thursday, Serbia's minister in charge of cooperation with the ICTY, Rasim Ljajic, revealed a hitch in the bid to track down Mladic, who was likely to be living under a fake identity.

'We have established that Mladic applied for an identity card in 1999 and got it, (but) that documentation, including his fingerprint, went missing,' Ljajic told B92 radio, adding that the authorities were probing the case.

The Blic newspaper reported that the file containing Mladic's fingerprint is crucial in an investigation into whether the former Bosnian Serb general has adopted a false identity.

Such a cover was used by two other war crimes fugitives Serbia has arrested in recent months, including Karadzic, who lived openly in Belgrade as Dragan Dabic, alternative medicine healer.

Both Mladic and Hadzic are believed to be hiding in Serbia.

Mladic, 66, is wanted for genocide, war crimes and crimes against humanity during his time as commander of Bosnian Serb military forces during the 1992-1995 war in Bosnia.

Karadzic, 63, the Bosnian Serb political leader, was arrested in Belgrade in July and transferred to the International Criminal Tribunal for the former Yugoslavia in The Hague, where he is awaiting trial.