A hard-line Serb leader warned Wednesday of more violence in Kosovo if the newly independent state moves to establish control in the Serb-populated north.
Milan Ivanovic, a Serb leader from the northern Kosovo town of Kosovska Mitrovica, said Kosovo's ethnic Albanian leaders are wrong to assume that they will be able to assert authority in predominantly Serb areas.
About 50,000 Serbs in the north have pledged not to recognize the new state and to continue to consider themselves part of Serbia.
Kosovo's ethnic Albanian leadership "can implement their presence only by force," Ivanovic said.
In Belgrade, Serbia's nationalist Prime Minister Vojislav Kostunica lashed out again at the United States and demanded that Washington reverse its recognition of Kosovo.
"As a nation and a state, we will put up resistance every day until the United States is convinced that the rule of international law must be re-established in the Balkans and the illegal declaration of the fake state (of Kosovo) is annulled," Kostunica said.
Kosovo's Prime Minister Hashim Thaci has ruled out a partition of the new country along ethnic lines. However, it is unclear how Kosovo's fledgling government might assert control in Serb-dominated areas.
Serbia and Kosovo's Serb minority have refused to accept the independence of Kosovo, an ethnic Albanian-dominated region that Serbs consider the cradle of Serbia's history and culture.
Belgrade and Kosovo Serbs have sought instead to keep control over the parts of Kosovo where the Serb minority lives, staging a wave of violent protests following the Feb. 17 declaration.
Some 2,000 people gathered in Kosovska Mitrovica on Wednesday, staging a peaceful rally as a pop band from Belgrade held a concert.
There are fears that the clashes over Kosovo independence could turn into a bigger conflict, similar to the ethnic wars in the region in the 1990s.
NATO troops have been in charge of controlling Kosovo's border with Serbia after Serb rioters pelted police with rocks and bottles during last week's protests. Nineteen officers were injured.
Serbs also have refused to accept a new European Union mission in Kosovo, saying it was designed to acknowledge Kosovo's independence. The mission staff evacuated from the Serb-held north but said they would return.
Belgrade also has rejected the EU mission, but has directed most of its anger at the United States.
Kostunica said in his statement that "the United States has taken on historic responsibility because it trampled on the international law that is the basis of the peace and stability in the world."
"It is possible that America thought ... Serbs are a minor nation," Kostunica added. "But Serbia will prevail, step by step, and it will win in the end."
Elsewhere, the man all but certain to win Russia's presidency warned Wednesday that Kosovo's independence could destabilize Europe.
Dmitry Medvedev, who is expected to easily win Sunday's presidential vote, said Kosovo's independence has "jeopardized security and stability of the vast region."
In Vienna, Irish Prime Minister Bertie Ahern said Serbs are "part of the European family" and reiterated the European Union's desire to deepen its relationship with Serbia.
"Recognition of Kosovo is not an expression of hostility towards Serbia," Ahern told a joint session of the OSCE's Permanent Council and Forum for Security Cooperation.