The Russian expulsion of a senior diplomat at the U.S. Embassy in Moscow was an “unprovoked” and escalatory move amid increasing tensions at the Ukrainian border, a White House spokeswoman said Thursday.

“Russia’s actions against our deputy chief of mission, who was a key member of the embassy’s leadership team, was unprovoked,” said White House deputy press secretary Karine Jean-Pierre. “Now, more than ever, it is critical that our countries have the necessary diplomatic personnel in place to facilitate communication between our governments.”