The Serbian parliament has voted overwhelmingly to condemn any attempt by Kosovo to become independent.
Vojislav Kostunica said Serbs in Kosovo should ignore independence
Authorities in the province say they will declare independence unilaterally in the coming weeks, because talks with Serbia have made no progress.
The Belgrade parliament's resolution calls for action against those who recognise an independent Kosovo.
The province is still formally part of Serbia, but has been administered by the United Nations since 1999.
The UN took over after a Nato-led assault drove out Serb forces who had been accused of persecuting Kosovo's ethnic Albanian population.
After eight hours of debate on Wednesday, Serbian MPs approved the resolution by 220 votes to 14.
It rejects the idea of the EU setting up a mission in Kosovo before the province's status is resolved.
The text also accuses Nato - which has 16,000 peacekeepers in Kosovo - of supporting ethnic Albanians, who account for about 90% of the population.
The resolution says Serbia will "reconsider" diplomatic ties with Western countries that recognise Kosovo's statehood.
The US and several EU states have indicated they may do so.
During the debate in parliament, Prime Minister Vojislav Kostunica accused the US of blocking efforts to find a compromise with ethnic Albanians by its open support of Kosovo's independence.
"America is openly striving for the destruction of the international order," Mr Kostunica said.
He added that Serbia would not join the EU if the bloc recognised Kosovo's independence.
"Serbia can join any integration only as a whole and not a truncated country," he said.
The opposition Liberal Party leader Cedomir Jovanovic - who does not oppose Kosovo's independence - said the resolution was a blow to Serbia's ambitions to become an EU member.