Tadic said in an interview with state television on Tuesday evening that the Mladic case was the toughest problem whose resolution was "the precondition for the resolution of all other problems."
"We have to integrate the activities of all services, and we cannot solve that problem without cooperation with international security and intelligence institutions," Tadic said, adding that fugitive Croatian general Ante Gotovina had recently been arrested thanks to coordinated efforts by Croatia and foreign intelligence agencies.
The daily Blic reported on Tuesday that intelligence officers from the Hague tribunal were also involved in the search for Mladic and that they had intercepted one of his telephone calls. The report was denied by the head of the Serbian Security and Information Agency (BIA) at a session of the parliament committee on security later that day.
Last week, Serbian war crimes prosecutor Vladimir Vukcevic said that several of Mladic's helpers had been identified and that criminal charges would be brought against them.
The arrest and handover of Ratko Mladic to the Hague tribunal is the main obstacle on Serbia and Montenegro's path to the European Union and NATO.