A swap would have significant consequences for efforts between Washington and Moscow to repair ties chilled by a deepening atmosphere of suspicion.
Ten people accused of spying for Russia were expected to appear in New York federal court Thursday afternoon, and many were expected to enter guilty pleas to charges that could set deportation proceedings in motion. An 11th person charged in the case is a fugitive after jumping bail in Cyprus.
Igor Sutyagin, a Russian arms control analyst serving a 14-year sentenced for spying for the United States, had told his relatives he was going to be one of 11 convicted spies in Russia who would be freed in exchange for 11 people charged in the United States with being Russian agents. They said he was going to be sent to Vienna, then London.
In Moscow, his lawyer, Anna Stavitskaya, said a journalist called Igor Sutyagin's family to inform them that Sutyagin was seen walking off a plane in Vienna on Thursday. However, she told The Associated Press she couldn't get confirmation of that claim from Russian authorities.
Russian and U.S. officials have refused to comment on any possible swap.
Attorney Robert Krakow, who represents defendant Juan Lazaro, said Thursday that Lazaro's actions Thursday would be motivated by a desire to be with his family. An attorney for defendant Anna Chapman, Robert Baum, said late Wednesday, "There's a good possibility that the case will be resolved at the initial court appearance tomorrow."
An attorney for defendant Donald Howard Heathfield, who was arrested in Massachusetts, said Wednesday, "if they can resolve the case, great," when asked why his client was being transferred to New York.
Special riot police had beefed up security around Moscow's Lefortovo prison early Thursday and a gaggle of TV cameras and photographers jostled for the best position to see what was going on. A convoy of armored vehicles arrived at the prison, thought to be the central gathering point for people convicted of spying for the West, including Sutyagin.
Police cars and prison trucks left the prison all morning, but it was unclear whether they carried any passengers.
"A swap seems very much on the cards. There is political will on both sides, and actually by even moving it as far as they have, Moscow has de facto acknowledged that these guys were spies," intelligence analyst Pavel Felgenhauer said Thursday.
Five of the suspects charged with spying in the U.S. were ordered to New York on Wednesday, joining five others already behind bars there, after Sutyagin was transferred from a forlorn penal colony near the Arctic Circle and spilled the news of the swap.
Dmitry Sutyagin said his brother remembered only one other person on the Russian list of spies to be exchanged — Sergei Skripal, a colonel in Russian military intelligence who in 2006 was sentenced to 13 years on charges of spying for Britain.
A spokesman for British Prime Minister David Cameron would not confirm or deny a possible London tie to the spy swap. "This is primarily an issue for the U.S. authorities," spokesman Steve Field said.
Defense lawyers in Moscow and New York have expressed confidence that their clients' fates would be settled very soon.
The 11 suspects were formally charged in a federal indictment unsealed Wednesday in New York. All were charged with conspiring to act as secret agents; nine were charged with conspiracy to commit money laundering. The indictment demanded that those accused of money laundering return any assets used in the offense.
"Of certain events tomorrow that might occur, the fact the indictment is minimal makes perfect sense. This is a crazy situation," Krakow said Wednesday.
Prosecutors released a copy of the indictment as federal judges in Boston and Alexandria, Va., signed orders directing that five defendants arrested in Massachusetts and Virginia be transferred to New York. All were charged in Manhattan.
The defendants were accused of living seemingly ordinary lives in America while they acted as unregistered agents for the Russian government, sending secret messages and carrying out orders they received from their Russian contacts.
All are in U.S. custody except for a man identified as Christopher R. Metsos, who is charged with being the spy ring's paymaster. Metsos, traveling on a forged Canadian passport, jumped bail last week after being arrested in Cyprus.
Sutyagin, who worked as an arms control and military analyst at the Moscow-based U.S.A. and Canada Institute, a think tank, was arrested in 1999 and convicted in 2004 on charges of passing information on nuclear submarines and other weapons to a British company that investigators claimed was a CIA cover. Sutyagin has all along denied that he was spying, saying the information he provided was available from open sources.
His case was one of several incidents of Russian academics and scientists being targeted by Russia's Federal Security Service and accused of misusing classified information, revealing state secrets or, in some cases, espionage.