The head of Russia's U.S. spying operations has defected, a Russian paper reported Thursday, potentially providing the West with one of its biggest intelligence coups since the end of the Cold War.

The Russian newspaper, Kommersant, identified the man as Col. Shcherbakov and claimed he was responsible for uncovering a Russian spy ring in the United States in June. The subsequent arrests of 10 spies humiliated Moscow and complicated a "reset" in ties with Washington.

The newspaper said Shcherbakov, whose first name it did not provide, had been responsible for "illegal spying" in the U.S., indicating spies operating under deep cover without diplomatic immunity. He fled to the United States in June, a few days before the FBI arrested spy Anna Chapman and her nine accomplices.

Gennady Gudhov, deputy chairman of the Russian parliament's security committee, confirmed the report, saying it was a major failure by Russian intelligence officials and a win for the United States.

"It is a major blow to the image of the Russian intelligence services," Gudhov told Reuters.

The newspaper also quoted a Kremlim official as saying a Russian hit squad was probably already planning to kill Shcherbakov.

"We know who he is and where he is," the unidentified official said, according to Kommersant. "Do not doubt that a Mercader has been sent after him already."

Ramon Mercader was the Russian assassin who murdered exiled Bolshevik Leon Trotsky with an ice axe in Mexico in 1940.