Robert King, the U.S. special envoy on North Korean human rights, is urging the release of American missionary Robert Park.
"It's one of the worst places in terms of lack of human rights," King told reporters after meeting South Korea's foreign minister. "The situation is appalling."
"Improved relations between the United States and North Korea will have to involve greater respect for human rights by North Korea," he added.
It is believed that North Korea detained Park after he illegally entered the country on Christmas Day.
King called on North Korea to release Park, but acknowledged that Washington had little information on him.
"We are actively working to find out where he is being held and to urge that he be released," King said. "We have requested that our protecting power in Pyongyang determine his condition and we have not heard yet what that is."
Park is 28 years old and from Tucson, Ariz.
He told friends he was going to enter North Korea to bring attention to the suffering there and help reunify the two Koreas.