Russia warned the United States in 2011 to stop trying to recruit its security agents as spies and expelled a CIA operative in January this year after Washington ignored the warning, the Federal Security Service (FSB) spokesman said.
Russia kept the expulsion in January quiet but went public this week when it detained Ryan Fogle, a U.S. diplomat it says was a spy, because it was fed up with the United States ignoring its concerns, Nikolai Zakharov said.
"The CIA crossed a red line and we were forced to react," Zakharov said.
In the biggest spy scandal between the former Cold War foes in three years, the FSB said on Tuesday that Fogle had been caught red-handed trying to recruit a Russian security officer as a CIA agent. He was ordered to leave Russia.
In October 2011, the FSB officially warned the CIA station chief in Moscow "that if provocative recruitment efforts aimed at Russian security service employees continued, the FSB would take 'mirror' measures," Zakharov said.
He said the FSB had named Russian officers who had been targeted and the CIA operatives who had approached them, adding that the U.S. director of national intelligence, James Clapper, had been "made aware of this issue".
"The CIA did not take our concern over the situation into account" and continued its recruitment efforts, he said.
The FSB played up the capture, providing television stations with footage of the American being detained in a blond wig and pinned to the ground, as well as pictures of disguises, a wad of cash and a letter offering a target up to 1 million euro a year.
It could hardly have come at a worse time, days after Russia and the United States announced plans to organize an international conference to seek an end to Syria's civil war.
FSB spokesman also added that last December, an American diplomat - like Fogle, a third secretary at the U.S. embassy in Moscow - had been caught trying to recruit a Russian agent, and had left the country on Jan. 15 after being declared persona non grata.