Kim Dong-chul, a 62-year-old naturalised US citizen born in South Korea, was arrested last October.
Kim had made an apparent confession in Pyongyang last month in front of reporters, saying he was paid by South Korean intelligence officers.
The US has previously accused North Korea of using its citizens as pawns in a diplomatic game. Pyongyang denies the accusations.
At the time of Kim’s arrest, the US State Department had said it would not be commenting on the case as speaking publicly about detained Americans can complicate the process of getting them released.