The US State Department announced today, Thursday, that Russia has expelled Bart Gorman, the deputy US ambassador in Moscow, and said that it is studying a response to this step, which it considered an escalation by Russia.

In response to Al Jazeera, the US State Department described the Russian move as unjustified and escalatory, and called on Moscow to stop expelling diplomats on flimsy grounds and work to build diplomatic missions.

The US State Department added to Al Jazeera, "We urgently need the appropriate diplomatic staff to facilitate communication with Moscow."

A US State Department spokesman told AFP that his country calls on Russia to stop the baseless expulsions of US diplomats, adding that the US side is studying a response to Gorman's expulsion.

It was not immediately clear why the second official at the US diplomatic mission in Moscow was expelled, but the move comes amid Western speculation of a possible Russian invasion of Ukraine.

In the past, the United States and Russia exchanged expulsion of diplomats and recall of ambassadors, after relations between them witnessed tensions over various issues such as accusations of Russia interfering in the US elections.