WASHINGTON (Reuters) - The United States has expelled two Russian embassy officials after Russia earlier expelled two U.S. diplomats from the American embassy in Moscow, the U.S. State Department said on Friday.

"In response to the Russian Federation's specious expulsion of two U.S. Embassy Moscow diplomats, the State Department reciprocated by declaring persona non grata two Russian Embassy officials operating in the United States," a State Department spokesman said.

"The Department will not tolerate the Russian government's pattern of harassment of our diplomats," the spokesman said, adding that "unacceptable actions against our Embassy personnel in Moscow will have consequences."

Russia's RIA news agency quoted an unnamed source in the Russian foreign ministry as confirming the expulsion, calling t groundless and saying Washington had used Moscow's Sept. 14 expulsion of two U.S. diplomats "caught red-handed engaging in spying activities" as a pretext.

"We are not interested in escalation, but if such hostile actions continue, as always, we will respond firmly and decisively," RIA quoted the source as saying.

Russia said on Sept. 14 that it was expelling two U.S. diplomats whom it accused of working with a Russian national charged with collaborating with a foreign state.

Relations between Moscow and Washington have plunged to their worst point in more than 60 years because of the war in Ukraine. The U.S. is providing advanced weaponry to Ukraine and has hit Russia with sanctions in response to its invasion in February 2022.

(Reporting by Simon Lewis and Ismail Shakil and Elaine Monaghan; Writing by Elaine Monaghan and Susan Heavey; Editing by Katharine Jackson and Sandra Maler)