Serb forces captured Vukovar in late 1991 after a three-month siege President Boris Tadic is to become the first Serbian leader to pay his respects to Croatian victims of a notorious 1991 massacre.
He will visit the town of Vukovar, which was captured after a three-month siege by the Serb-led Yugoslav army.
Mr Tadic will lay wreaths at a memorial commemorating the murder of 260 hospital patients.
He and Croatian President Ivo Josipovic will also go to a graveyard where 18 Serb villagers were killed by Croats.
Croatia has described the event as an attempt to relax relations between the two countries.
But a number of Croatian right-wing parties and war veteran groups have called for protests, arguing that Mr Tadic is trying to avoid apologising for the massacre in Serbia’s name because his visit is taking place in an “unofficial” capacity.
Earlier this year, the Serbian president went to Bosnia to commemorate more than 8,000 Muslim men and boys killed by Serb forces at Srebrenica in 1995.
This article is from the BBC News website. © British Broadcasting Corporation, The BBC is not responsible for the content of external internet sites.