The state-run KCNA news agency said suspicions about "hostile acts" by Matthew Todd Miller and Jeffrey Edward Fowle had been confirmed by evidence and their testimony.
"The relevant organ of the (North) is carrying on the investigation into them and making preparations for bringing them to court on the basis of the already confirmed charges," it said.
Miller, 24, was arrested in April after he apparently ripped up his visa at immigration and demanded asylum in the communist state.
Fowle, who entered the North on April 29, was arrested later after he reportedly left a bible at a hotel, bringing to three the number of Americans held by the isolated state.
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A number of foreigners -- many missionaries -- have been arrested in the reclusive communist state in the past.
Some were allowed to return home after intervention by high-profile US figures, but efforts to secure Bae's release have so far been unsuccessful.
A 75-year-old Australian, John Short, was also detained for nearly two weeks until early March after distributing religious material in the capital Pyongyang.