The White House says US President Barack Obama is deeply concerned about a North Korean court sentencing two American journalists to 12 years in a prison camp.
Inside the camps, prisoners are forced to do hard labour and to survive on meagre rations.
Laura Ling and Euna Lee were arrested 12 weeks ago while producing a documentary on refugees fleeing the Stalinist state for Current TV, a Californian station co-founded by former US vice-president Al Gore.
Taken to Pyongyang they were put on trial for illegally entering the closed Stalinist state and for unspecified hostile acts.
A White House spokesman said President Barack Obama was deeply concerned by the sentences handed out to Ms Lee and Ms Ling, adding the United States is using all possible channels to secure their release.
Pyongyang says the women illegally set foot on North Korean territory but supporters of the journalists say they were on the Chinese side of the border, and that has been backed up by their cameraman, who managed to escape.
He has backed their story that North Korean border guards arrested the pair on the Chinese side of the border.
They were detained along the Tumen River, which marks part of the border between China and North Korea.
The sentences are certain to heighten tension between the US and North Korea, which are running high after the communist regime conducted a nuclear test last month.