Former Bosnian Serb general Ratko Mladic rejected the charges put to him by the UN War Crimes Tribunal in The Hague on Friday and refused to enter a plea, DPA reported.
The International Criminal Tribunal for the Former Yugoslavia (ICTY) allowed him 30 days to enter his plea, setting July 4 for his next appearance.
But the man held primarily responsible for the slaughter of 8,000 Muslim men and boys at Srebrenica in 1995 said he needed longer.
"I would like to receive what you read out just now - these obnoxious charges levelled against me," Mladic said, speaking in Serbian.
"I want to read these properly to give it some proper thought together with my lawyers because I need more than a month."
Earlier he told the court he was seriously ill before a summary of the indictment was read out to him by presiding judge Alphons Orie.
"I am a gravely ill man," he said, indicating that he had not read any of the material - including his indictment - that had been presented to him after he was taken to ICTY's Scheveningen prison in The Hague on Tuesday.
Appearing defiant, he said he did not want "a single word or sentence" of his indictment to be read out to him.
Mladic, dressed in suit and tie, entered the chamber wearing a baseball cap. He later took it off, revealing a bald head. On Thursday, his lawyer in Belgrade claimed he had received chemotherapy for cancer of the lymph nodes in 2009.
The former general's voice was trembling slightly but he answered all the questions put to him by Orie.
He challenged the court's assertion that he was born on March 12, 1942. "That is not my date of birth," he said, claiming he was born "on Good Monday, 1943."
"Then we will further verify that," Orie said.
Mladic is accused of genocide for the massacre of 8,000 men and boys in Srebrenica and other atrocities committed during the 1992-1995 Bosnian civil war, as well as of war crimes and crimes against humanity.