The talks leading to the largest U.S.-Russian spy swap since the Cold War began when CIA director Leon Panetta approached Russia’s spy chief with a proposed deal, a U.S. official says.

Shortly after the FBI arrested the 10-person Russian spy ring, officials at the U.S. intelligence agency reached out, leading the way for Panetta to suggest the exchange. The U.S. official said both sides wanted a speedy resolution of the case, which could have cast a pall over improving U.S.-Russian relations.

Panetta had already developed “a sound relationship” with Mikhail Fradkov, head of Russia’s Foreign Intelligence Service, that allowed the two former adversaries to quickly clinch the deal, the U.S. official said. The 10 Russian sleeper agents were traded for four prisoners Russia accused of spying for the U.S.

Other U.S. government figures helped Panetta negotiate the diplomatic angles of the talks, the official added, speaking on condition of anonymity to discuss sensitive intelligence matters.

The official added that the CIA and FBI already “basically knew everything about the Russian network when we rolled it up.” He said that while the United States could have followed through with all the charges and locked the spies up for years, it was clear the 10 Russian agents were more valuable as trade bait.

Because they had never penetrated the U.S. government, the official said, they could not reveal any sensitive information. The official would not confirm whether anyone in the ring had ever handled classified information.

The suspects pleaded guilty to the least serious charges against them — of being unregistered foreign agents.

The official added that the swap should help remove an “irritant” that could have been an obstacle to U.S.-Russian relations, but that no one expects the Russians to stop spying.

Former CIA analyst and 50-year-plus agency veteran Charlie Allen said it was clear that Moscow and the White House did not want the spectacle of a long drawn out trial of 10 “illegals” to derail the resetting of U.S.-Russian relations after years of friction.

The positive yield for U.S. intelligence, he said, is the signal it sends that the U.S. will bring in from the “real cold of Russian prisons … individuals we can never abandon.” He was referring to “The Spy Who Came in from the Cold,” the 1963 John Le Carre novel that described Cold War espionage.

Allen said the CIA’s relocation program for such spies “is quite good. It was once terrible.” He did not elaborate.

“It does not mean that the intelligence activities will be diminished on either side, and it does not mean that the Russians will not continue to run ‘illegals,’ “ he said. “Illegals are in the Russian services DNA,” he said, “and, rest assured, the SVR will continue.”

Allen spoke after a fundraising gala, in honor of the CIA’s fallen, headlined by Dan Akroyd Thursday night. The spy swap was the talk of the event, held by the Intelligence and National Security Alliance.