Washington has called for an amnesty and the "immediate release" of a Korean-American tour operator who has been sentenced to 15 years of hard labor in North Korea.
U.S. State Department spokesman Patrick Ventrell made the statement in Washington on May 2.
"There is no greater priority for us than the welfare and safety of U.S. citizens abroad and we urge the DPRK (Democratic People's Republic of Korea) authorities to grant Mr. Bae amnesty and immediate release," Ventrell said.
U.S. citizen Kenneth Bae -- known in Korea as Pae Jun Ho -- was arrested in November 2012 and was sentenced on May 1, following a one-day trial on April 30.
Pyongyang has not explained the charge of "committing hostile acts" against Bae, but North Korean state media claimed he had admitted his guilt.
Ventrell added that Swedish diplomats -- which curate U.S. interests in North Korea because Washington and Pyongyang do not have diplomatic relations -- were not able to attend Bae's trial and have not seen him since April 26.
The human rights watchdog Amnesty International says Bae, 44, has had no access to lawyers.
Amnesty has called for Bae's release unless he is retried by an independent court.
It is not known where Bae will serve his sentence.
Analysts have speculated that Pyongyang is using Bae as a bargaining chip in order to open up a dialogue with Washington.
Relations between the United States and North Korea have been particularly strained since the North conducted a long-range rocket launch just over a year ago and a third nuclear weapons test in February.
International disarmament talks between North and South Korea, the United States, Japan, Russia, and China collapsed in 2009. Since then, the United Nations has imposed several rounds of sanctions against North Korea.
With reporting by AFP and AP