The lawyer said she did not know which one of the 10 alleged Russian spies arrested in the US would be exchanged for the prisoner in Russia.

Sutyagin, the American spy, would initially be sent to Britain under the swap deal, Stavitskaya said.

Hearing cancelled

Meanwhile a bail hearing for three of the alleged spies was cancelled in Virginia, as two other alleged spies waived their right to a local hearing in Boston and were being sent to New York.

The Russians are charged with acting as illegal agents of a foreign government [Reuters]

The alleged spies captured in the US are accused of being deep cover agents for Russia's SVR intelligence agency who were tasked with infiltrating US policymaking circles.

They were not assigned to collect classified, secret information, a justice department official said, and have been charged with acting as illegal agents of a foreign government, rather than espionage, and money laundering offences.

They were instead apparently tasked to learn about a broad swath of topics including nuclear weapons, US arms control positions, positions on Iran, White House rumours, CIA leadership turnover, the last presidential election, congress and political parties

In 2009, for example, two of the accused, Richard and Cynthia Murphy, were asked by Moscow to provide information about the US negotiating position on the START arms reduction treaty as well as Afghanistan and the approach Washington would take in dealing with Iran's suspect nuclear programme.

Under the present charges the suspects could face up to 25 years in prison.