Radovan Karadzic, the former Bosnian Serb leader, has asked the international tribunal in The Hague to replace the judge in charge of the preparatory stage of his trial.
In a letter released by the The Hague tribunal on Tuesday, Karadzic said that Alphons Orie, the presiding judge, had a "personal interest" in convicting him.
Karadzic said the Dutch judge participated in previous trials against Bosnian Serbs and would want the rulings in those cases reinforced to justify "draconian" sentences against them.
"There clearly cannot be any question of impartiality on his part,'' Karadzic said in a letter dated last Friday to Fausto Pocar, the president of the Yugoslav war crimes tribunal.
Karadzic said Orie would be interested in having that sentence "upheld and somehow validated, which could be achieved through, inter alia, partial and biased conduct of the case against me".
Karadzic also wants the other judges of Orie's chamber replaced.
Judge Orie presided over Karadzic's first appearance at the International Criminal Tribunal for the former Yugoslavia (ICTY) on 31 July - since his capture in Belgrade after 11 years in hiding.
Karadzic declined to enter a plea, but must do so when he appears in court again on August 29. If he declines again, a "not guilty" plea will be entered on his behalf.
Karadzic listed 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 prison.
Judge Orie also was on the tribunal that convicted Milan Babic, a Croatian Serb leader, who committed suicide in the tribunal's detention unit in 2006. Oria is also currently among the judges trying Vojislav Seselj, a Serb nationalist leader.
Karadzic is accused of allegedly organising the 1995 massacre of more than 8,000 Muslims in Srebrenica and other atrocities in the Bosnian war, including genocide.
Judge Orie, a former criminal lawyer and justice of the Dutch supreme court, has been a judge at the UN tribunal since 2001.
Preliminary stages of tribunal cases are conducted by a single judge, but trials are heard by a panel of three. The tribunal has no juries.