The spokesman for the tribunal, Refik Hodzic said on Friday that hunger-striking Seselj would probably not be able to give instructions to his court-appointed lawyers for the 6 December session, which was why the main hearing was postponed.
The first session within the main hearing was held last Monday, but the indictee was not present.
"The Tribunal expresses its grave concern about the actions of the accused Vojislav Seselj, who by refusing to accept food, medicine, and medical care while in the custody of the Tribunal's Detention Unit is seriously jeopardizing his health," according to a press release issued on the tribunal's web site.
The 52-year-old Serb ultranationalist, accused of war crimes against Croats, Bosniaks and other non-Serbs, has been declining food and medical care since 11 November 2006.
"In view of the Tribunal's obligation and commitment to safeguard the physical well-being of persons placed into its custody, Seselj was yesterday (on Wednesday) moved from the Detention Unit to the adjoining Dutch prison hospital where additional medical facilities and staff are available. This was done to allow for his health to be monitored more closely and to guarantee prompt medical intervention should a medical necessity arise," the press release read.
The tribunal adjourned the case explaining that "the trial chamber cannot exclude that the medical condition of the accused will deteriorate to such a degree where, even if he would wish to do so, the accused would be unable to instruct assigned counsel."
Serbia's Prime Minister Vojislav Kostunica on Friday wrote to the tribunal president, Fausto Pocar, urging him to try to prevent "irremediable consequences" for Seselj's health.
"In Dr. Seselj's case, the Serbian government is deeply concerned at the possibility of a violation of basic rights guaranteed to every human being -- the right to a defence chosen by the accused and the most fundamental right to life," the Serbian premier said.