The sting operation that foiled a plot aimed at smuggling a shoulder-fired missile (search) to U.S.-based terrorists marked "a new stage in cooperation" between the intelligence services of former Cold War (search) foes the United States and Russia, a Russian intelligence official said.

Russian officials tipped off the FBI (search) about a Briton of Indian descent who they said was seeking weapons to buy in St. Petersburg, Russia. Months later, the operation culminated with the man's arrest Tuesday in Newark, N.J., where he was allegedly was trying to seal the deal.

The sting was the result of improved cooperation among the secret services of Russia, Britain and the United States, said Sergei Ignatchenko, chief spokesman of the Federal Security Service -- the successor of KGB (search).

"It is the first time such an operation has been carried out since the ends of the Cold War, when our special services acted in confrontation with each other," Ignatchenko said in Washington, the Russian state news agency ITAR-Tass reported Wednesday.

"This action marks a new stage in the development of cooperation between the special services of these countries," he said.

U.S. officials said the suspect was planning to sell an SA-18 Igla missile (search) capable of downing a commercial airliner to a man he thought was a terrorist. The putative buyer turned out to be an undercover FBI agent and the weapon was an inoperable copy brought from Russia aboard a ship to make the deal seem real, U.S. officials said.

Two other men, believed to be involved in money laundering, were apprehended about the same time as the British suspect at what was described as a gem dealership on Fifth Avenue in New York City, according to a federal law enforcement official who spoke on condition of anonymity.

The official said the British suspect is Hemat Lakhani. He will be charged with material support of terrorism and weapons smuggling, the official said.

The Briton did not appear to be connected any known terrorist group, and authorities stressed there was no specific, credible threat to shoot down an airliner in the United States.

In Moscow, the FSB and the Kremlin declined to comment on the operation, which Ignatchenko said was conducted by the FBI in conjunction with the FSB.

According to state-run Rossiya television, Ignatchenko said the operation was a "positive result" in efforts to stop the activities of criminal groups involved in illegal arms sales.

The operation came ahead of a summit expected this fall between President Bush and Russian President Vladimir Putin and struck a positive note on weapons proliferation, an issue that has raised differences between the two countries.

Putin, who was a KGB agent during the Cold War, threw his support behind the United States in the fight against terrorism following the Sept. 11 attacks. He has repeatedly said that battling terrorism and arms proliferation are areas where cooperation with the West is crucial to world security.

Yevgeny Volk, head of the Heritage Foundation's Moscow office, said the trade in Russian-made shoulder-fired missiles was "a very big business and a very profitable one."

The arrest "demonstrates the cooperation of the secret services, but from the point of view of stopping the flow of these weapons, it is not so effective."

"I believe that both Russia and America felt they needed a piece of public relations to show they are closely cooperating in combatting terrorism and the illegal arms trade," said Volk.

In June, Russia's defense minister called for stricter controls on exports of shoulder-fired missiles, saying they are dangerous weapons that too often fall into terrorist hands.