Karadzic, 64, faces life imprisonment on 11 counts of genocide, war crimes and crimes against humanity for his actions as president during the 1992-95 Bosnia war that claimed an estimated 100,000 lives.
The trial before the International Criminal Tribunal for the former Yugoslavia (ICTY) starts next Monday, but Karadzic claims it is being rushed.
“I hereby inform you that my defence is not ready for my trial that is supposed to begin as scheduled, on the 26th of October, and that therefore I shall not appear before you on that date,” he said in a written submission to the court.
The news came as Sweden said another former Bosnian Serb president, Biljana Plavsic, will be freed from prison in Sweden on October 27, following an ICTY decision to grant her early release from her sentence ordered for persecuting Croats and Muslims.
Karadzic, who denies all the charges against him and insists on conducting his own defence, complained of “unequal, disproportionate and unjust circumstances” in preparing his case.
Thirteen years on the run
“No lawyer in this world could prepare a defence within this period of time,” he asserted.
“This trial, being the most gigantic, should have been given at least the average time for preparation, which is almost two years.”
Court spokeswoman Nerma Jelacic said the trial would start as scheduled.
“The trial hearing in the case of Radovan Karadzic will proceed on Monday, 26 October at 09:00 in Courtroom 1 as previously scheduled,” she said in a statement.
The judges are expected to decide at that time the next steps in the proceedings.
A heavily-bearded Karadzic was arrested on a Belgrade bus in July 2008, while posing as an alternative healer, after 13 years on the run.
Massacre at Srebrenica
He is accused of being one of the masterminds of a plan to “permanently remove” Bosnian Muslims and Croats from Serb-claimed territory in Bosnia-Hercegovina.
Along with his military henchman Ratko Mladic, who is still at large, he is especially blamed for the 44-month siege of Sarajevo that left 10,000 people dead and the July 1995 massacre of around 8,000 Muslim men and boys at Srebrenica.
Prosecution spokeswoman Olga Kavran said the team was “ready to start the trial”.
“The most important thing is that the trial will take place, if it is not Monday, it will be later.”
Karadzic has filed several requests to delay his trial, saying in September he needed 10 more months to study a million pages of prosecution evidence and the statements of hundreds of witnesses.
“My entering the proceedings under such circumstances would be my only crime, for which I would deserve contempt of all victims of the war and a curse of the generations to come,” said his letter to the court.
ICTY trial boycotts
Several other accused have boycotted their ICTY trials, though never with forewarning.
One of them, ultra-nationalist Serb leader Vojislav Seselj, refused to leave his cell for the November 2006 opening of his trial, which was eventually delayed by a year.
Ex-Serb intelligence chief Jovica Stanisic was absent from the start of his trial on March 17, 2008, for reasons of ill health. The courtcase eventually under way this June.
In Sweden, Plavsic, 79, was sentenced in February 2003 to 11 years behind bars for her role in a campaign of persecution against Croats and Muslims in the Bosnian war.
She is the highest ranking official of the former Yugoslavia to have acknowledged responsibility for atrocities.