Bisset said that Milosevic had made efforts to ensure the acceptance of proposed peace agreements and that he played a crucial role in securing the signing of the Dayton accords that ended the war in 1995.
The witness cited the Cutilheiro Plan, which he said would have prevented the war had it not been rejected by Bosnian Muslim leader Alija Izetbegovic, allegedly at the suggestion of the then US ambassador Warren Zimmerman.
Bisset described allegations that Milosevic started the wars in order to create a Greater Serbia as sheer fantasy, insisting that the accused actually tried to preserve the Yugoslav federation.
Prosecutor Geoffrey Nice challenged the witness's credibility, quoting several of his statements in which he called the ICTY a Stallinist court and compared Chief Prosecutor Carla del Ponte to Hitler's prosecutor.
Nice cited a statement made by the witness regarding anti-Milosevic demonstrations in Belgrade in 1996, when Bisset said that Milosevic would sell anyone just to stay in power. He also said that Bisset had written about ruthless methods used by the Serbian police and military against ethnic Albanian insurgents in Kosovo in 1999.
Also on Friday, the ICTY rejected Milosevic's request for provisional release to undergo medical treatment in Moscow.
The trial is scheduled to continue on Monday with testimony by a new defence witness.