Transcript for Russia to officially charge US man with espionage: Reports

In the meantime, next, to American man held in Moscow's most infamous dungeon. Tonight, he's now been formally charged with being a spy. A Russian lawyer working for Paul Whelan, a former U.S. Marine, says he will fight the charges. But this question tonight, is this all an effort by the Russians to get an exchange for someone here? ABC's chief global affairs correspondent Martha Raddatz again tonight. Reporter: Tonight, reports Russia officially bringing espionage charges against Paul Whelan, accusing the former marine of being an American spy. Whelan now held in isolation in a notorious Moscow prison. His lawyer, calling the charges "Baseless." Still, he believes Whelan will be convicted to facilitate a prisoner exchange, postally for marina butina, now locked in a Virginia detention center after pleading guilty to being a Russian agent. A Russian news site with ties to the security services claims Whelan was caught with a classified list of Russian operatives, saying that Whelan had been spying for the U.S. For ten years, trying to recruit Russians through interset chatrooms and social media. Whelan's lawyer is speculating that surveillance began long before MARIA butina pleaded guilty, but it certainly seems more than a coincidence that they arrested Whelan now, with some American officials believing this is strictly retaliation and that Whelan was an easy target because of his travels to Russia. David? All right, Martha Raddatz reporting live tonight. Thank you, Martha.

This transcript has been automatically generated and may not be 100% accurate.