During a status conference, defendants Cermak and Markac will enter their plea, via video link, on the amended indictment confirmed on 14 December 2005, Milenov said at the weekly press briefing.
Cermak and Markac, who have been provisionally released pending trial, will enter a plea only on two new counts of the indictment.
The amended indictment includes two new and seven old counts, charging the two generals with murder and inhumane treatment.
The two men are charged with crimes against humanity and violations of laws or customs of war committed against Serbs rebels in Croatia during and after Operation Storm between 4 August and 15 November 1995.
Asked if the ICTY prosecution would move for the joinder of the Markac-Cermak indictment with that of general Ante Gotovina, spokeswoman for the prosecution Florance Hartmann said she was unable to answer that question in advance, adding that more would be known on Friday.