Ratko Mladic has appeared in a Serbian court hours after being arrested following 16 years on the run.
Authorities want to extradite the former Bosnian Serb army chief to the war crimes tribunal in The Hague.
He was found in a village in northern Serbia where he was living under an assumed name, Milorad Komodic.
General Mldaic, 69, faces accusations including a genocide charge over the killing of about 7500 Bosnian Muslim men and boys at Srebrenica in 1995.
He was also in command during the siege of Sarajevo which lasted three-and-a-half years during which 10,000 people died.
Serbian television showed footage of him after the arrest, wearing a baseball cap, looking frail and walking slowly.
The hearing was halted on Thursday due to his poor health and pending a medical examination, his lawyers said. Court officials believe he will appeal. The whole process is expected to take a week.
Following the arrest of Radovan Karadzic in 2008, General Mladic became the most prominent Bosnian war crimes suspect at large.
Serbia had been under intense international pressure to arrest him and send him to the UN International Criminal Tribunal to the former Yugoslavia in The Hague.
His lawyer Milos Saljic told reporters the judge had tried to question General Mladic but the suspect was in a "difficult psychological and physical condition", and was unable to communicate.
The hearing is expected to resume on Friday.
General Mladic asserts that he does not recognise the authority of the UN war-crimes tribunal, Mr Saljic said.
Axel Hagedorn, a lawyer representing the families of the victims of Srebrenica, says they have been waiting for years for this arrest.