The Biden administration on Friday ordered two Russian diplomats expelled from the United States in retaliation for the expulsion of two U.S. diplomats from Moscow last month.

The State Department said it had taken the action in response to Russia declaring the two American diplomats persona non grata because of contacts with a Russian national who had once worked for the now-closed U.S. consulate in Russia’s far-eastern city of Vladivostok and was arrested this year.

“The department will not tolerate the Russian government’s pattern of harassment of our diplomats,” spokesman Matthew Miller said in a statement. “Unacceptable actions against our embassy personnel in Moscow will have consequences.”

The expulsions come at a time of animosity between Washington and Moscow over the war in Ukraine and as diplomatic relations have plummeted to their worst level since the Cold War.