Some final check-ups have to be made before the request is sent to Australian authorities, said the head of the Justice Minister's cabinet, Mario Kresic.
The documents charging Vasiljkovic were compiled by the Sibenik County Court and the Ministry received them on 23 January.
The former commander of Serb paramilitary units in Croatia, who now holds Australian citizenship, was arrested in Sydney on the basis of an international arrest warrant issued by Croatia.
The Australian media have said that Vasiljkovic's attorneys have announced an appeal with the Supreme Court, claiming that their client's detention is unlawful and contrary to the Australian Constitution.
A local court in Sydney ruled detention for Vasiljkovic without right to bail until the first hearing on January 27.
Croatia has 60 days to issue a formal extradition request, after which a federal judge will decide if Vasiljkovic can be extradited.
The 51-year-old Vasiljkovic is charged, in his capacity as commander of a special Serb paramilitary unit, with torturing and killing captive Croatian soldiers and police in a prison in Knin in June and July 1991 as well as in Bruska near Benkovac in February 1993.
He is also charged with devising, in agreement with a commander of the former Yugoslav People's Army (JNA), a plan of attacks in the Glina area resulting in the destruction of civilian facilities, the expulsion of the local population, the plundering of their property, and the killing and wounding of civilians, including a foreign journalist.