Russia's Foreign Ministry says the decision by the United States to suspend the operations of Syria's embassy in Washington and consulates in other cities was "worrying and disappointing."
Washington on March 18 closed down the embassy, citing the illegitimacy of President Bashar al-Assad's regime.
The ministry said in a statement issued on March 19 that Washington had renounced its "co-sponsor" role in negotiating peace in Syria by closing down the embassy.
Syria's government, meanwhile, said on March 19 that the closure of the embassy was arbitrary and illegal.
Worsening relations between the United States and Russia over Ukraine in recent months have diminished efforts by the two countries to broker a peace deal in Syria, which is in its fourth year of civil war.
Based on reporting by Reuters, AFP, and Interfax