Kosovo looked forward on February 18 to recognition by the Western powers who went to war to save its Albanian majority, but Russia served notice the new state will never be forced on its Serb allies in the territory.
Fireworks brought to a close a day of celebration in the Kosovo capital Pristina, where parliament adopted a declaration of independence from Serbia and proclaimed the new Republic of Kosovo a sovereign state.
Kosovo's 2 million Albanians were left guessing which country would be first to recognise the sixth state to be carved from Serb-dominated former Yugoslavia, closing a long chapter in its bloody demise.
European Union foreign ministers meet on Monday to discuss Kosovo's secession. Swift recognition is expected from Britain, Germany, France and Italy as well as the United States.
Proposing the independence declaration to parliament, Prime Minister Hashim Thaci said Kosovo would be a country of "all its citizens", a gesture to the 120,000 Serbs still living here.
But Serbia and Russia swept that aside.
"We'll strongly warn against any attempts at repressive measures should Serbs in Kosovo decide not to comply with this unilateral proclamation of independence," Russia's U.N. ambassador, Vitaly Churkin, said ahead of an emergency session of the U.N. Security Council, called by Moscow.
Serbs in Kosovo, led by the Serb-dominated north and with the full backing of Belgrade, reject the territory's secession, reinforcing an ethnic partition that NATO and the United Nations have failed to erase since the 1998-99 war.
Protests were called for midday on Monday (1100 GMT) in Serb towns in Kosovo. Some analysts have long predicted that de facto, although not legal, partition has been Belgrade's "Plan B" all along.
ALL AVENUES EXHAUSTED
Most of the EU's 27 members will recognise Kosovo and will underwrite it with a 2,000-strong rule-of-law mission to take over supervision of the new state from the United Nations. But at least six EU members are reluctant.
In New York, seven Western countries on the U.N. Security Council said the body could not agree on the future of Kosovo.
But they said February 17 events marked the end of a process "that has exhausted all avenues in pursuit of a negotiated outcome".
Almost two years of Serb-Albanian negotiations ended in December with neither side giving ground on the key issue of sovereignty.
Kosovo Albanians say there is no going back after Serb forces killed thousands and drove out almost one million in a two-year war against separatist guerrillas. NATO bombed for 11 weeks in 1999 to force a withdrawal of Serb forces, and the United Nations took control.
The Serb-dominated north has resisted attempts by the U.N. mission to extend its writ north of the River Ibar.
The new EU mission will face the same challenge. That was underlined within hours of Saturday's declaration by hand grenades lobbed at EU and U.N. buildings in the Serb stronghold of Mitrovica.
"In the next period Serbia will function as a state in Kosovo in the areas where Serbs live as the majority," Serb Minister for Kosovo Slobodan Samardzic said in Mitrovica, speaking in English. "It is so because Serbs recognise only one state, and that is Serbia."