The United States has expressed deep concern over North Korea’s sentence of 12 years in a labor camp for the two American journalists.

In a statement Monday, U.S. State Department spokesman Ian Kelly said Washington is engaged through all possible channels for the release of Laura Ling and Euna Lee.

Kelly urged Pyongyang to free them immediately on humanitarian grounds while expressing sympathy for the families of the detained journalists.

The two female journalists are from former U.S. Vice President Al Gore's San Francisco-based Current TV. They were taken into custody on March 17th by the North at the Chinese border for illegal entry and unspecified “hostile actions”.

Former Vice President Al Gore has yet to make a response on the North’s sentence.