The White House and State Department neither confirmed nor denied reports of a mission by Carter to bring home Aijalon Mahli Gomes, who was jailed in April for illegally crossing North Korea's border with China.

Unnamed senior administration officials were quoted by CNN as saying Carter was headed to North Korea Tuesday. One described him as "someone in a position to take action as a distinguished international figure."

Foreign Policy magazine first reported the mission by Carter, 86, on Monday, citing officials who stressed the private and humanitarian nature of the bid which comes at a time of high tension in US-North Korean relations.

Asked about the reports, State Department spokesman Philip Crowley said: "Obviously, there's been lots of reporting on this subject over the past 24 hours."

"We will continue to withhold comment. We do not want to jeopardize the prospects for Mr. Gomes to be returned home by discussing any details related to private humanitarian efforts to get him released and back here safely to the United States."

White House spokesman Bill Burton similarly declined to confirm the Carter mission, saying he would not comment "on anything that could have a negative impact on any private humanitarian mission that might be happening."

"We obviously think that Mr. Gomes should be released. There will be more information on that in the future."

The former president's Atlanta-based Carter Center also did not respond to requests for comment.

The United States has repeatedly voiced concern about the health of Gomes, whom two American doctors and a US consular official visited earlier this month in a Pyongyang hospital. But they were unable to secure his release.

Gomes, a 30-year-old former English teacher in South Korea and reportedly a devout Christian, was arrested in January. He was sentenced in April and fined the equivalent of 700,000 dollars.

A family spokeswoman on Tuesday also declined to confirm Carter's mission.

"We are grateful for the medical care given in North Korea," said the spokeswoman, Thaleia Schlesinger.

"The family is hoping and praying that the government of North Korea will grant him amnesty and return him home on humanitarian grounds," she said.

North Korea state media said in July that Gomes tried to commit suicide and was being treated in a hospital.

Gomes was "driven by his strong guilty conscience, disappointment and despair at the US government that has not taken any measure for his freedom," the communist state's official news agency said.

Tensions between Washington and Pyongyang, already high over failed international efforts to halt North Korea's nuclear weapons program, worsened markedly after accusations that a North Korean submarine sank a South Korean navy ship in March, killing 46 sailors.

The Foreign Policy report said Carter would be traveling as a private citizen, similar to the mission carried out by former president Bill Clinton last year when he secured the release of Americans Laura Ling and Euna Lee, two television journalists who were also jailed after wandering across the North Korean border with China.

Carter made an unprecedented visit to Pyongyang in 1994 when the United States came close to war with North Korea over its nuclear program. He helped defuse the crisis through talks with then-leader Kim Il-Sung.

In March this year during a visit to Seoul, the former president urged South Korea and the United States to hold direct talks with Pyongyang, saying a failure to negotiate nuclear disarmament might lead to a "catastrophic" war.

Carter, a Democrat and former peanut farmer, served as US president from 1977 to 1981.

He has gone on to make a career in diplomacy, and as an elder statesman has been vocal about issues such as Israeli-Palestinian peace negotiations, humanitarian strife in Zimbabwe and the situation in war-torn Darfur.

Carter was awarded the Nobel Peace Prize in 2002.