U.S. Defense Secretary Lloyd Austin on Thursday accidentally referred to Russia as the Soviet Union while speaking during a visit to Seoul, South Korea.

RUSSIA ORDERS SOME US EMBASSY STAFF TO LEAVE COUNTRY

Austin was answering a question about how the U.S. plans to respond to potential Russian aggression at the Ukraine border, saying any U.S. response would be made in collaboration with the international community during a press conference.

Ahn Jung-hwan/Yonhap via AP

South Korean President Moon Jae-in, right, bumps elbows with U.S. Defense Secretary Lloyd Austin before their meeting at the presidential Blue House in Seoul, South Korea, Thursday, Dec. 2, 2021. (Ahn Jung-hwan/Yonhap via AP)

"Whatever we do will be done as a part of an international community. The best case though is that we won't see an incursion by the Soviet Union into the Ukraine," Lloyd said, referring to Russia but accidentally calling it the "Soviet Union," Reuters reported.

BLINKEN WARNS RUSSIA: US WILL USE ‘HIGH IMPACT’ ECONOMIC TACTICS TO DETER AGGRESSION AT UKRAINE BORDER

Secretary of Defense Lloyd Austin pauses while speaking during a media briefing at the Pentagon, Wednesday, Nov. 17, 2021, in Washington.  (AP Photo/Alex Brandon)

The Soviet Union, which formed in the 1920s, collapsed in the early 1990s after the fall of the Berlin Wall.

Ukraine, which has claimed Russia has deployed about 90,000 troops to its border, was once a Soviet republic but is currently developing plans to join the European Union and NATO, Reuters reported.

Russian President Vladimir Putin attends a flower-laying ceremony at the Russian Civil War memorial on Unity Day, in Sevastopol, Crimea, on Nov. 4, 2021. (MIKHAIL METZEL/SPUTNIK/AFP via Getty Images)

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Secretary of State Antony Blinken on Wednesday said he has spoken with virtually all of the 29 other NATO members and they had voiced support in stopping Russian aggression.

Russian officials on Wednesday ordered U.S. Embassy staff who had been in Moscow for three years or more to leave the country amid growing tensions between the two nations — likely in response to Washington's decision to send 50 Russian diplomats home in June, according to The Wall Street Journal.