"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.