Russia’s ambassador in the United States will depart Washington Saturday for urgent consultations in Moscow, the embassy said, warning that bilateral ties were on the brink of “collapse.”

Moscow’s strained relationship with Washington hit a new low Wednesday when Russia called back its ambassador over comments made by U.S. President Joe Biden who likened his Russian counterpart to a “killer.”

“On March 20, Ambassador of Russia to the United States Anatoly Antonov is leaving for Moscow for consultations,” the embassy said in a statement early Thursday.

The comments were aired as the U.S. Commerce Department announced it was toughening export restrictions imposed on Russia as punishment for jailed Kremlin critic Navalny’s poisoning.

Moscow last recalled its U.S. envoy for consultations in 1998 over a Western bombing campaign in Iraq.

In 2014, during the fallout from Russia’s annexation of Crimea from Ukraine, Putin said that recalling a U.S. envoy would be “a measure of last resort.”