Kenneth Bae, a missionary arrested in November 2012 and jailed for 15 years, admitted to wrongdoing and called on the US government to help secure his freedom so that he could return to his family "at the earliest possible date."
US State Department spokeswoman Jen Psaki said Washington remained "very concerned" about Bae's health and was actively working to release him.
"We continue to urge the DPRK authorities to grant Bae amnesty and immediate release," Psaki said, referring to the North by its official name, the Democratic People's Republic of Korea.
Another US official who requested anonymity voiced hope that putting Bae in front of reporters signalled North Korea's "willingness to release him."
The official said that Robert King, the US envoy on human rights in North Korea was prepared to bring Bae home.
"We have offered to send ambassador King to Pyongyang to secure Mr. Bae's release. We have asked the North Koreans this, and await their early response," the official said.
King had been invited to North Korea to discuss Bae's case at the end of August last year, but Pyongyang rescinded the invitation at the 11th hour without explanation.
Bae, a Korean American also known as Pae Jun-Ho, was arrested as he entered North Korea's northeastern port city of Rason.
He was sentenced to 15 years of hard labor last year on charges of seeking to topple the government.
Bae spoke Monday to a small group of reporters in Pyongyang at what was described as a news conference.
The 45-year-old was dressed in a gray inmate's uniform for the event, which lasted three and a half minutes.
Bae apologised and acknowledged to participating in anti-government acts -- a public confession that observers saw as a pre-requisite for any release.
Family 'gravely concerned' for Bae
US Vice President Joe Biden said recently that Bae had been jailed for no reason -- a comment Bae appeared to allude to when he spoke of unhelpful comments that might block his release.
It was not possible to determine whether Bae had been coerced into holding the press conference, or to what extent his remarks were scripted for him.
A court in North Korea, which strictly controls religion, had described Bae as a militant Christian evangelist who had smuggled subversive material into the country and sought to establish a base in Rason.
Bae's family, which has campaigned hard for his release, said they were encouraged to see him in "decent health" but remained "gravely concerned" about his overall condition.
"I am sure he is worn down physically and emotionally ... In his eyes, I could see he was distressed," his sister Terri Chung said in a statement.
Addressing the leaders in Pyongyang, the statement said the family understood Bae had been convicted of crimes under North Korean law and "sincerely apologises" on his behalf.
In the past, North Korea has released detained Americans after visits by former presidents Bill Clinton and Jimmy Carter.
There is no US embassy in Pyongyang and the only American to have had any regular contact with the new North Korean leader Kim Jong-Un is the former NBA star Dennis Rodman.
North Korea has, in recent months, sought to push the United States into agreeing to resume six-party talks on the North's nuclear programme, but Washington insists Pyongyang must first show a tangible commitment to denuclearisation.
In Seoul on Tuesday, US Deputy Secretary of State William Burns said the US shared South Korean concerns about "further reckless behavior and provocations in the future" from the North.
North Korea recently released another American, 85-year-old Merrill Newman, a few weeks after the Korean War veteran was pulled away during an organized tour and accused of crimes against the regime.
Newman made a videotaped confession in stilted English that he later said was involuntary.