MOSCOW, Feb 7 (Reuters) - Russia has demanded that the U.S. embassy in Moscow stop spreading what Moscow regards as fake news regarding its military operation in Ukraine and has threatened to expel U.S. diplomats, the TASS news agency reported on Tuesday.

The warning included a harsh message to Lynne Tracy, the new U.S. ambassador to Moscow, TASS said, citing a senior Russian foreign ministry source who said Tracy had been told she must strictly adhere to Russian law when making any statements about Russia's armed forces in Ukraine.

U.S. diplomats engaged in what Moscow called "subversive activities" would be expelled, TASS quoted the source as saying.

A U.S. State Department spokesperson confirmed that the U.S. embassy had received a diplomatic note from the Russian foreign ministry, but said the department's general policy was not to comment on diplomatic correspondence.

Russia has made "discrediting" its armed forces a crime punishable by up to five years in jail, while a charge of knowingly distributing "false information" about the military carries a maximum sentence of 15 years.

Tracy arrived in Moscow last month. Feb. 24 will mark the first anniversary of President Vladimir Putin's decision to send tens of thousands of troops into Ukraine in what he calls a "special military operation".

Ukraine and its Western allies accuse Putin of launching an unprovoked colonial-style war of aggression and reject his assertion that the operation is designed to protect Russia's own security from NATO's eastern enlargement.