The White House vowed Thursday to "deal with" Russia's decision this week to expel dozens of American diplomats, declaring the move a "further deterioration" in relations between the two countries.

President Trump Donald John TrumpBubba Wallace to be driver of Michael Jordan, Denny Hamlin NASCAR team Graham: GOP will confirm Trump's Supreme Court nominee before the election Southwest Airlines, unions call for six-month extension of government aid MORE's top spokeswoman, Sarah Huckabee Sanders, defended the United States's move to join more than two dozen other nations and NATO allies in expelling scores of "undeclared Russian intelligence officers" over an attack on a spy that has been linked to Russia.

Sanders said while the Western response to the Russian poisoning attack on a former double agent living in Britain was "appropriate," Russia's retaliatory response Thursday "marks a further deterioration in the United States-Russia relationship."

"Russia’s response was not unanticipated, and the United States will deal with it," the White House statement added.

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The comments were the latest from the Trump administration warning of a response to Russia's expulsion of 60 U.S. diplomats. State Department spokeswoman Heather Nauert said earlier Thursday that Washington would "reserve the right to respond" to the move.

Exactly what action the U.S. could take to push back on the latest move from Russia is unclear. Still, the warnings underscore the deepening tensions between Washington and Moscow after Russia was blamed for the poisoning of a former Russian spy and his daughter with a military-grade nerve agent on British soil earlier this month.

Trump announced on Monday that the U.S. would kick out 60 Russian officials believed to be intelligence agents and shutter the Russian consulate in Seattle in retaliation for the poisonings. Two dozen other countries also expelled Russian diplomats.

The Russian government has denied any role in the poisonings in the U.K., and has accused the U.S. of running a "colossal blackmail" campaign against Moscow.

Russian Foreign Minister Sergei Lavrov announced a response to the expulsions of Russian officials on Thursday, saying that 60 American diplomats would be booted out of Russia and that the U.S. consulate in St. Petersburg would be closed.

Other countries that expelled Russian diplomats, he said, would face similar measures from Moscow.

The diplomatic tit for tat put on display the rising tensions between Russia and the West at a time when many officials in Europe and the U.S. are under pressure to combat Moscow's efforts to meddle in foreign elections.