Lawyers for Ratko Mladic are due to lodge an appeal to prevent his extradition to the Hague to face war crimes charges.
A panel of judges will then look at the case and make a decision, which could see the former Serbian wartime leader on his way to the Netherlands as early as Tuesday.
The Mladic family maintain the 69-year-old is mentally unstable and unfit to face trial.
The Serbian Radical Party, whose leader is in the dock at the Hague, held a demonstration in the capital Belgrade on Sunday in support of the man dubbed the butcher of the Balkans.
Around 180 people were arrested and 32 police officers injured as clashes broke out as evening fell.
Mladic, indicted for genocide following the deaths of 8,000 Muslim men and boys in Srebrenica, has been on the run for 16 years.