A defiant Ratko Mladic has refused to acknowledge "obnoxious" allegations that he orchestrated some of the worst atrocities of the Bosnian war during his prior life as the Serb military chief.

On Friday, Mladic told a UN courtroom that he did not want to hear "a single letter or sentence" of the indictment against him for genocide and war crimes committed during the 1992-95 war.

Mladic is accused of involvement in the ethnic cleansing purges of non-Serbs, a four-year shelling and sniping campaign in Sarjevo, and the infamous massacre of 8,000 Muslim boys and men who were slain in Srebrenica in 1995.

In court, Mladic claimed he was defending "my people and my country" during the war and he declined to enter pleas on the 11 war crimes charges listed in the indictment.

At the end of his hearing, he said: "I am Gen. Mladic and the whole world knows who I am."

When Mladic refused to co-operate with the court, presiding judge Alphons Orie set a new hearing for July 4.

The July hearing will give Mladic another opportunity to enter pleas on the charges he is facing.

If he fails to co-operate at that point, the court will enter "not guilty" pleas on his behalf and begin preparing for a trial.

A trial could take years to complete and it is not clear how the 69-year-old Mladic's health will hold up.

Mladic has said he wants to "live to see that I am a free man."

Since the end of the war, Mladic's family says he suffered two strokes while living as a fugitive.

His lawyer has also claimed that Mladic has been fighting lymph node cancer in recent years and spent nearly three months in hospital in 2009 while being treated.

In court on Friday, Mladic told the judge he is "gravely ill," but he did not elaborate on his health while in earshot of the public.

When he did speak to the court, Mladic's speech was slow and seemed slightly slurred. And he appeared unable to fully use his right hand.

His worn-out appearance has drawn sympathy from some members of the public, even from those who believe Mladic should be facing trial.

"I can't believe that they forced him to stand the trial now," Belgrade resident Borko Jancic, who said Mladic looked old and frail, told The Associated Press.

Dragan Tosic, who watched the court proceedings in a Belgrade café, said Mladic looked "pretty good, considering the whole situation."

Tosic said "this should have happened a long time ago."

But others, like Munira Subasic, the head of the Mothers of Srebrenica Association, expressed a strong desire for Mladic to finally face justice.

"Happy to be here to see, once again, the bloody eyes of the criminal who slaughtered our children in 1995," she said. "And I am sad because many mothers didn't live to see this -- mothers who found bones belonging to their children, buried them without heads and hands and the only wish they had was for him to be arrested. But they didn't live to see it."

With files from The Associated Press