Lawyers for former Bosnian Serb leader Radovan Karadzic face a deadline Friday to file an appeal against his extradition to The Hague tribunal to face war crimes charges.
His lawyer says he will mail the documents five minutes before the post office closes.
Serbian authorities arrested Karadzic on Monday in Belgrade, where he had lived openly, practicing alternative medicine under the name Dragan Dabic.
Officials say they tracked him down by following people thought to be helping him avoid capture.
The United Nations war crimes tribunal has charged Karadzic with genocide and crimes against humanity for his efforts to ethnically-cleanse Bosnia-Herzegovina of Muslims and Croats during the Balkan conflict of the 1990s.
The charges include the 1995 Srebrenica massacre of about 8,000 Muslim men and boys. The charges also include his role in the siege of the Bosnian capital, Sarajevo, by Serb forces during which snipers, shellfire, disease and starvation killed thousands.
With the Karadzic arrest, the Balkan war-crimes tribunal's top fugitive targets now are former Bosnian Serb military chief Ratko Mladic, and ex-Croatian Serb leader Goran Hadzic. Former Bosnian Serb police commander Stojan Zupljanin was arrested last month in Serbia.
Some information for this report was provided by AFP and Reuters.