His visit to Kosovo on Sunday marked the first time a Serbian head of state has entered Kosovo since it became a UN protectorate at the end of the 1998-1999 war.
"I am against the independence of Kosovo and for me, it is unacceptable. I will never accept such a solution," Tadic told some 2000 Serbs gathered to greet him in the central Kosovo town Strpce.
Tadic said his trip was designed to remind the world of the plight of Serbs in Kosovo, the historic heartland of Serbian culture and religion.
The visit comes before long-awaited talks on Kosovo's final status, expected to start later this year under UN auspices.
Kosovo Albanians demand independence but Belgrade insists that the province remains part of Serbia.
Tensions between Albanians and
Serbs have been high since 1998
Speaking to the Serbian state television from the village Velika Hoca, Tadic said he had invited UN Kosovo chief Soren Jessen-Petersen to visit Belgrade "to work together on solving problems" in Kosovo.
"The Serbs here live in isolation which seems insurmountable. The only thing we can do is to give our utmost to overcome this difficult situation," Tadic said.
More than 200,000 Serbs have fled Kosovo since the UN took control at the end of the war, when ethnic Albanian separatists battled Serbian forces under then-Yugoslav president Slobodan Milosevic.
In Pristina, police cordoned off the UN headquarters during the meeting between Tadic and Petersen as a small group of protesters demanded Serbia account for people still listed as missing from the war.
Demonstrators tried to pelt Tadic with eggs, but local police surrounded him and safely took him out from the UN compound. Two demonstrators were detained, police said.
"I did not come with a magic wand. I wish I did, but I can promise you that I will use all my powers and authority to fight for the rights of our people and every citizen living in Kosovo," Tadic told the villagers.