The UN war crimes tribunal in The Hague has rejected a request by Slobodan Milosevic to be allowed to go to Russia for medical treatment.
Mr Milosevic's health problems have delayed his trial
The former Yugoslav president, on trial for alleged war crimes, has high blood pressure and a heart condition.
The court said his lawyers had not satisfactorily proved that Mr Milosevic's medical needs could not be met in the Netherlands.
It also said it feared Mr Milosevic might not return to continue the trial.
Mr Milosevic, 64, is facing charges of genocide and other war crimes.
A court statement noted that he was in the final stages of a very lengthy trial which could result in life imprisonment in the event of a guilty verdict.
"In these circumstances, and notwithstanding the guarantees of the Russian Federation and the personal undertaking of the accused, the trial chamber is not satisfied... that the accused, if released, would return for the continuation of the trial."
Prosecutors also suspect that Mr Milosevic's wife and son live in Moscow, Reuters news agency said.
The presiding judge agreed with the prosecution that if Mr Milosevic wished "to be treated by specialists who are not from the Netherlands, such physicians may come here to treat him".
The trial at the International Criminal Tribunal for the former Yugoslavia has entered its fourth year.
It has been frequently interrupted by Mr Milosevic's ill health.
Before he won the right to conduct his own defence in 2003, proceedings had been interrupted 15 times.
Mr Milosevic faces charges of war crimes and crimes against humanity for his alleged central role in the wars in Bosnia, Croatia and Kosovo during the 1990s.
He also faces genocide charges over the 1992-95 Bosnia war, in which 100,000 people died.
Mr Milosevic was in office for 13 years until 2000.