By Lim Chang-Won

SEOUL, Wednesday 25 August 2010 (AFP) - Former US president Jimmy Carter was heading to North Korea Wednesday on a mission to win the release of an American serving eight years of hard labour in the isolated communist state, media reports said.

Carter, accompanied by his wife and Carter Center president John Hardman, is expected to arrive in Pyongyang later Wednesday, South Korean cable news network YTN reported.

The Nobel peace laureate may leave Pyongyang on Thursday with Aijalon Mahli Gomes, who was jailed in April for for illegally crossing into the North from China, the Munhwa Ilbo newspaper said.

Washington has neither confirmed nor denied reports of Carter's mission, which comes at a time of high tensions on the peninsula following the sinking of a South Korean warship in March with the loss of 46 lives.

Carter, now 86, made a landmark visit to Pyongyang in 1994 when the United States came close to war with North Korea over its nuclear programme. He helped defuse the crisis through talks with then-leader Kim Il-Sung.

He is said to be travelling as a private citizen, similar to the mission 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.

White House spokesman Bill Burton said 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 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.

The North's official news agency said in July that Gomes tried to commit suicide and was being treated in a hospital.

He was "driven by his strong guilty conscience, disappointment and despair at the US government that has not taken any measure for his freedom," it said.

Foreign Policy magazine first reported Carter's trip on Monday, citing officials who stressed its private and humanitarian nature.

One unnamed senior US administration official was quoted by CNN as saying Carter was "someone in a position to take action as a distinguished international figure".

State Department spokesman Philip Crowley said Washington would continue to withhold comment.

"We do not want to jeopardise 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."

The Atlanta-based Carter Center did not respond to requests for comment.

A spokeswoman for the Gomes family also declined to confirm the mission.

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

"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.

Tensions between Washington and Pyongyang, already high over failed international efforts to halt North Korea's nuclear weapons drive, deteriorated after accusations that a North Korean torpedo sank the South Korean corvette.

On a visit to Seoul in March, Carter 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.