The United States on Monday said it is expelling 12 Russian diplomats in New York, an act Russia’s ambassador to the United Nations described as “hostile.”

Olivia Dalton, a spokeswoman for the U.S. mission to the United Nations, accused the diplomats of “engaging in espionage activities that are adverse to our national security” and said they “abused their privileges of residency in the U.S.” The expulsions were in “the works for several months,” she added, and not because of the Russian invasion of Ukraine.

Vassily Nebenzia, Russia’s ambassador to the United Nations, said the U.S. is violating its commitments as the host of U.N. headquarters in New York City. He also promised that Russia will respond to the “hostile” expulsions. White House Press Secretary Jen Psaki replied during a Monday afternoon press conference that she believes “the hostile act is committing espionage activities on our own soil.”