Serbia's election commission has barred US and British observers from monitoring the presidential election in the country on 20 January.
Kosovo's future is likely to be a major issue during the polls
Observers from the two nations were unwelcome because of their backing of Kosovo's drive for independence from Serbia, some commission members said.
The province is expected to declare independence in the next few months.
Serbia's commission approved monitors from the Organisation of Security and Co-operation in Europe and from Russia.
The commission failed to reach the required majority to approve the US and British monitors during a vote in Belgrade, Serbian officials were quoted as saying by Reuters.
They said this was because of opposition from representatives of Prime Minister Vojislav Kostunica's Democratic Party of Serbia.
Mr Kostunica has repeatedly criticised London and Washington for their support of the independence plans of Kosovo.
Serbia's ultra-nationalist Radical Party - whose members abstained during the vote - accused the US and Britain of trying "to destroy us and take away our territory".
The US and most members of the 27-member EU back independence for Kosovo, while Serbia and Russia fiercely oppose it.
Kosovo has been run by the United Nations since 1999, when Nato intervened to end Serb persecution of ethnic Albanians, some of whom had taken up arms.
The future of the majority ethnic Albanian province is likely to be an important issue in the electoral campaign.
Current Serbian President Boris Tadic is expected to face a strong challenge from the Radical Party candidate, Tomislav Nikolic.