The two were found guilty of a "grave crime" against North Korea and of illegally crossing into the reclusive nation's territory, according to North Korea's state-run news agency.

Former U.N. Ambassador Bill Richardson on Monday called the sentencing part of "a high-stakes poker game" and said the time might be right for the United States to work out the release of Laura Ling and Euna Lee with the country's leaders in Pyongyang.

"It is harsher than expected," Richardson said on NBC's "Today" show.

At the White House, deputy spokesman William Burton said in a statement: "The president is deeply concerned by the reported sentencing of the two American citizen journalists by North Korean authorities, and we are engaged through all possible channels to secure their release."

Richardson, who was instrumental in negotiating the release of U.S. citizens from North Korea in an incident in the 1990s, said "the good thing is that there is no charge of espionage." He also said now that the legal process has been completed, he thinks negotiations for their "humanitarian release" can begin.

Richardson said officials of the Obama administration had been in contact with him for his thoughts on how to proceed.