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Russia will expel 60 American diplomats and close the U.S. consulate in Saint Petersburg, the Kremlin announced Thursday — a severe escalation in tensions between the two superpowers that comes in response to the Trump administration's expulsion of Russians earlier this week.

The U.S-Russia expulsions — together, one of the largest since 1986 — threaten to uproot how the two countries have worked together in numerous delicate international situations, including the conflict in Syria and nuclear tensions on the Korean Peninsula.

The Russian Foreign Ministry announced the move Thursday, saying in a statement that Foreign Minister Sergey Lavrov had summoned Jon Huntsman to notify him that Russia would be kicking out 58 employees of the U.S. embassy in Moscow and two of the U.S. consulate in Yekaterinburg — a tit-for-tat reaction to the U.S. decision to order Russian diplomats out over the poisoning of an ex-Russian spy in Britain.

The Russian Ministry also said that Lavrov told Hunstman he was shutting down the U.S. consulate in St. Petersburg in direct retaliation for the American decision to close the Russian consulate in Seattle, leaving Moscow with no presence on the American West Coast.

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Moscow's action appears to be disproportionate response: Saint Petersburg is the second-largest city in Russia and a popular tourist destination, and the U.S. consulate there is the oldest American mission in Russia.

Lavrov said Russia would be applying the same response to other nations that also expelled Russian diplomats this week.

"Based on the principle of reciprocity, in response, 58 employees of the US Embassy in Moscow and two employees of the U.S. Consulate General in Yekaterinburg were declared 'persona non grata' for activities incompatible with diplomatic status," Russian Deputy Minister of Foreign Affairs Sergey Ryabkov said in the statement.

Ryabkov said the diplomats must leave by April 5 and that the consulate in Saint Petersburg must be closed by March 31.

State Department spokeswoman Heather Nauert said at a press briefing that the U.S. would not rule out responding further to Russia's latest action, signaling the possibility of a further escalation.

"We reserve the right to respond," she said.

On Monday, the U.S., the U.K., NATO and 25 other countries announced the expulsion of dozens of Russian diplomats in response to the poisoning of ex-Russian spy Sergei Skripal in British that was allegedly orchestrated by the Kremlin.

The U.S. said it would dismiss 60 Russian diplomats identified by officials as intelligence officers, as well as close Russia's Seattle consulate. Twelve of those to be expelled were from the Russian mission to the UN, while 48 were from other places throughout the U.S. The individuals have one week since the announcement to leave.

In total, over two days, the U.S., U.K., NATO and the 27 other countries, including Georgia, previously part of the Soviet Union, expelled a total of 153 Russian diplomats in a show of solidarity with Britain.

These steps, a senior Trump administration official told reporters on the condition of anonymity Monday, were intended to let the Russian government know that "when you attack our friends, you will face serious consequences."

Removing these Russians, the official said, is also a bid to reduce the "unacceptably numerous" Russian intelligence officers who reside in the United States and spy on Americans.