Mr Karadzic argues that he will not receive a fair trial at The Hague
Former Bosnian Serb leader Radovan Karadzic has asked the UN war crimes tribunal to replace the judge in charge of the preparatory stage of his trial.
In a letter to The Hague tribunal, he said presiding judge Alphons Orie had a "personal" interest in convicting him.
Mr Karadzic said the Dutch judge would convict him to reinforce rulings in his earlier cases against Bosnian Serbs.
Mr Karadzic is indicted on 11 counts of war crimes in connection with the 1990s Bosnian war, including genocide.
Alphons Orie has been a UN tribunal judge since 2001
Judge Orie presided over Mr Karadzic's first courtroom appearance at the International Criminal Tribunal for the former Yugoslavia (ICTY) on 31 July - just days after his capture near Belgrade.
Mr Karadzic - who had been more than a decade on the run - then declined to enter a plea.
"There clearly cannot be any question of impartiality on his [Judge Orie's] part," Mr Karadzic said in the letter made public by The Hague tribunal on Tuesday.
He cited a number of cases involving Judge Orie, including the conviction of Momcilo Krajisnik, the former Bosnian Serb parliament speaker, who was sentenced to 27 years in jail.
Eleven counts of genocide, war crimes, crimes against humanity and other atrocities
Charged over shelling Sarajevo during the city's siege, in which some 12,000 civilians died
Allegedly organised the massacre of up to 8,000 Bosniak (Muslim) men and youths in Srebrenica
Targeted Bosniak and Croat political leaders, intellectuals and professionals
Unlawfully deported and transferred civilians because of national or religious identity
Destroyed homes, businesses and sacred sites
Mr Karadzic argued that the Dutch judge would now be keen on having that ruling "upheld and somehow validated, which could be achieved through, inter alia, partial and biased conduct of the case against me".
Mr Karadzic is due to appear in court again on 29 August.
He led the formation of a separate Bosnian Serb assembly in 1991 - one of the sparks that ignited the 1992-1995 Bosnian war.
He had remained president of the Bosnian Serb Republic (Republika Srpska) until 1996, despite having been indicted for war crimes the year before.