Belarus has ordered 10 US diplomats to leave the country amid a row sparked by Washington's criticism of alleged human rights abuses, according to the US embassy in the capital Minsk.
The Belarussian foreign ministry said on Wednesday that the US officials had been declared persona non grata and must leave within 72 hours.
"In accordance with the Vienna Convention on diplomatic relations we will do everything so that the US diplomats leave the country during this period," Jonathan Moore, the US head of mission, said.
Moore is the highest ranking US diplomat in Minsk after the ambassador left last month.
"For the United States, the political prisoners in Belarus are much more important than the number of American diplomats in Belarus," he said.
Washington has said it could resume dialogue with the Belarus government if it were to release Alexander Kozulin, an academic who was jailed for five and a half years for helping organise protests against the election of Alexander Lukashenko, the president.
The Belarussian foreign ministry has reduced its diplomatic staff at its own embassy in Washington to six, including the ambassador, and ordered the expulsions after the US embassy in Minsk failed to follow suit.
Sean McCormack, the US state department spokesman, said that the move was "unjustified and unwarranted".
Washington and the EU have already imposed sanctions on Belarus, including a travel ban on Lukashenko over his imprisonment of political prisoners and restrictions on democratic freedoms.
Belarus previouly reduced its embassy staff in Wahsington from 32 to 17 in protest at the US sanctions whic hit the state-controlled oil and chemicals company Belneftekhim.
Minsk says that the restrictions violate international law.