MOSCOW -- An American man who is being held in Moscow on suspicion of spying is due in court.

Paul Whelan, a former U.S. Marine, was arrested in Moscow at the end of December. The arrest raised speculation that he could be swapped for one of the Russians held in the U.S., such as gun rights activist Maria Butina, who has pleaded guilty to acting as a foreign agent in the U.S.

Whelan is to appear in court on Tuesday where the judge is expected to extend his arrest.

Spying charges carry a prison sentence of up to 20 years in Russia.