Both Serbia and Bosnia-Herzegovina say they will request the extradition from Britain of a Muslim member of Bosnia's wartime presidency.
Ejup Ganic was arrested late Monday at London's Heathrow Airport on a Serbian warrant and will be held until a hearing that is set for 29 March.
Serbia accuses Ganic of taking part in a 1992 ambush on a Yugoslav army convoy that was retreating from Sarajevo, in which at least 18 soldiers were killed.
Serbian Justice Minister Snezana Malovic said Tuesday her office is sending an official request to Britain shortly.
A spokesman for Bosnia's Prosecutor's Office Boris Grubesic said Bosnian prosecutors also are sending an urgent request for Ganic's extradition. He said Bosnia is entitled under international law to process its citizens suspected of war crimes.
Bosnian officials have criticized Ganic's arrest and say it will not only strain relations between the two Balkan neighbors, but also the inter-ethnic relations within Bosnia.
During the 1992-1995 ethnic conflict in Bosnia, Belgrade politically and militarily supported Bosnian Serbs.
Serb authorities accuse 19 former Bosnian officials of having a role in the 1992 ambush of the Yugoslav Army convoy. They say more than 40 people were killed in the attack.
Ganic, a professor of engineering, served as president and vice president of the Bosnian Federation between 1997 and 2001.
Under the 1995 Dayton peace accords, Bosnia was divided into two entities - the Muslim-Croat Federation and the Bosnian Serb Republic. Ethnic tensions remain high.
Some information for this report was provided by AFP, AP and Reuters.