On Friday EU officials urged the Serbian government to catch Mladic by the April 30 deadline or face a halt in talks on closer ties with the bloc.
"The situation seems to be very clear: unless Ratko Mladic is in The Hague by the end of the month (April), then we will have no other option but to disrupt the negotiations," said Olli Rehn, the EU Enlargement Commissioner.
Mladic, the former Bosnian Serb military chief, is charged with genocide over the 1995 Srebrenica massacre of about 8,000 Muslim men and boys and the siege of Sarajevo.
He has remained at large for more than 10 years since being indicted by the UN's Hague war crimes tribunal.
The Srebrenica massacre is seen as the single worst atrocity in the continent since World War II.
Rasim Ljajic, Serbia's human rights minister, who is in charge of cooperation with the Hague tribunal, said on Sunday that Serbia had information on 130 people who had helped hide Mladic over the years.
However, most of those people were in the Serbian part of Bosnia-Hercegovina, the minister told a Serbian newspaper.
"We have more information than before ... we have made progress but the European Union will only appreciate the result, not our efforts," the minister said.
Nato has also urged Serbia to arrest Mladic as well as find a positive solution for Kosovo in order to eventually pave the way for Serbia's acceptance within the North Atlantic alliance.
"See that Mladic gets to The Hague, and I can tell you that Nato will bring you in very quickly, then you can continue stabilisation and association with the European Union," Jaap de Hoop Scheffer, the Nato secretary-general, told a forum in Brussels on transatlantic relations.
Mladic is wanted for the killing
of 8,000 Bosnian Muslims
Meanwhile, an official of an intergovernmental organisation working for democracy and security of the Balkan region, has said that Mladic could be handed over to court of The Hague on May 10.
Ehrard Busek, the special co-ordinator of the Stability Pact for South Eastern Europe, said in a German newspaper at the weekend that "the latest information that I have received is that Belgrade now plans to hand him over on May 10".
"The longer the delays, the less credibility Belgrade will have," Busek said, urging the EU to put more pressure on Serbia to co-operate.
"They should be harder and act on their words," he said.
Failure to capture Mladic would mean the suspension of negotiations on an EU association agreement with Serbia, which would offer the country membership prospects along with trade priviledges and closer political ties.
Serbia has persistently denied knowledge of Mladic's whereabouts, although it recently admitted he had been under military protection until mid-2002 and received a pension from Belgrade until last December.
According to an analyst who once attended Serbia's military academy with Mladic, he has remained free from justice thanks to a small but loyal network of well-connected aides.