Mesic expressed optimism regarding the admission of those countries to the EU provided that each candidate did its part of the job.
There should not be double standards (for the admission) as they could only shake our confidence in the European Union and could also negatively affect bilateral relations between EU hopefuls, Mesic said at the 16th summit of central and southeastern European leaders.
Commenting on the summit meeting's topics - Economy, Energy and European Integration - Mesic appealed for joint actions against problems caused by the economic crisis and shortages in energy supplies.
On the margins of the conference, Mesic met Italian President Giorgio Napolitano for talks on the Croatian-Italian relations and their economic cooperation particularly in tourism. They also considered Croatia's EU membership bid.
According to the Office of President Mesic, the two presidents agreed that their countries had developed very good bilateral relations.
Napolitano reaffirmed his country's backing to Croatia's entry into to the EU as soon as possible and urged for a speedy removal of Slovenia's blockade on Croatia's EU membership talks.
Earlier on Friday, Serbian President Boris Tadic told the summit that the European Union could become a space of true safety and stability only with the full integration of the western Balkans with the bloc.
He described the Balkan region as a potential bridge in providing end-users with energy supplies from other parts of Europe.
At the summit President Vaclav Klaus of the Czech Republic, the current chair of the 27-strong EU bloc, said that his country fully supported western Balkan countries' EU aspirations.
Commenting on a Croatian-Slovenian border dispute which has led to a standstill in Croatia's EU membership talks, Klaus said that he would like to see bigger progress in the negotiating process, describing the Croatian-Slovenian border row as a bilateral issue.
Most countries have similar experiences with sensitive territorial issues, but no country should adopt solutions under pressure as such solutions are as bad as unilateral ones, Klaus said.
The summit drew leaders of Austria, Bosnia-Herzegovina. Bulgaria, Croatia, the Czech Republic, Italy, Macedonia, Moldova, Montenegro, Poland, Serbia, Slovakia, Slovenia and Ukraine.