"Independent Kosovo would be a precedent and it would become a problem for regional stability, not only in the Balkans but also in other regions of the world," Tadic said after talks with European Commission President Jose Manuel Barroso.
He stressed Belgrade had not yet decided whether or not it would attend the talks between representatives of Kosovo and Serbia, which UN special envoy Marrti Ahtisaari scheduled for 24 July in Vienna.
"We are prepared to attend the talks, but we expect Ahtisaari to send us conditions for the negotiations," Tadic said.
The international community wants the issue of Kosovo's final status to be solved by the year's end.
Tadic and Barroso also talked about Serbia's cooperation with the International Criminal Tribunal for the former Yugoslavia. The European Commission discontinued negotiations with Serbia in May on the country's Stabilisation and Association Agreement with the EU over Serbia's failure to fully cooperate with the UN tribunal at The Hague.