The Romanian and Bulgarian governments have joined Hungary in refusing to let Russia use their airspace to transport military supplies and personnel to Kosovo.
A Bulgarian government spokeswoman Stoyana Georgieva said Bulgaria would reconsider once Russia and NATO had created a unified command.
Russia replied by saying both Bulgaria and Hungary are violating international standards.
A BBC correspondent says the ex-communist countries do not wish to damage their prospects of closer union with the West by supporting what could be an independent Russian military initiative in Kosovo.
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